For some reason after completing the game character level does not update on bnet and thus we are not allowed to join nightmare games or higher even if we are the proper level but we can host the game properly. Whats up with that?

You can host new difficulty as soon as you beat diablo regardless of level. Not sure what you mean with it failing to update your level.

He means that even if his character is level 30+, any class, in the new "Global" Battle.net server the character always shows up as a level 1 Warrior.

You're misunderstanding what i'm saying here, you can't join games of a higher difficulty there is a bug which does not allow you to. You can host the game just fine but I'm not trying to play MP solo on a service that used to work in the way that I expect it to. Attempting to join a game on bnet gives you the error that your character must be level 20/30 in order to join nightmare/hell difficulty respectively even if your character IS that level or higher.

Edit: Thank you Realpsojed, didn't realize you commented before I replied and yes that is indeed what i mean.

I dont understand why Blizzard/GOG are selling this fantastic game if it has a lot of multiplayer Bug.
A lot of us bought Diablo 1 to play in Batlle.Net

patches sofar: 1. i dont have win 10 :D
2. wasnt interested in the online version , only local play so in my case nothing was fixed , but its okay:
cant play anything , CPU is at 70 - 90% after i cliked on the classical option to run, and thats bad for the hardware
Anyway, looks like it 's not gonna work, thats why i uninstalled it

Same issue, cant play public games in nightmare or hell due to chat channels showing characters as level 1

This is why we need to get this issue sorted fast cause it is a massive problem if you can't even play the higher difficulties with friends. If this post dies off then nothing will be fixxed. Yeah the B.Net account system does not seem to be updating the personal levels or classes of the account made. Which is causeing a conflict with the restrictions of the games systems of level 20 for nightmare and level 30 for hell, making it impossiable to join a game hosted by firends even if you reached level 50 already. So you are in the small minority of people that don't seem to upgrade their computer and only wanted to play single player, but the majority of people those fixes did help. I have no idea how old your pc is if diablo 1 is useing up over 70 - 90% of your CPU o.O but yeah you really need to step out of the dark ages XD.

In pre-GOG Diablo, this was not the case. The rule was that the creator must meet the same level requirement as the joiners. Beating the Dark Lord would often, but not necessarily, entail gaining enough experience that you would meet the level requirement for the next difficulty as a side effect - but you did not need to beat the Dark Lord to move on. I seem to recall people who were pursuing a 3@30 that would not fight the Dark Lord at all until their fight at level 30 on Hell difficulty.

The GOG release seems seems to be almost completely unchanged from classic, so I'd be a bit surprised if this rule were changed here. Have you confirmed that a character of level less than 20 can create a Nightmare game?

My friend and I both finished normal together and are both over level 20 but can not join each others games when we host nightmare, so what is your explaination for that one?

Game can be hosted but not joined.

Please fix this.

If you finished Normal, then you should have beat The Dark Lord and also have a dot, no? My post above was that having a dot is not required. If you have a dot, then it doesn't matter whether I am right about that particular non-requirement, because you satisfy it anyway.

There are several threads running about how everyone is treated as a level 1 warrior on the new battle.net. I don't recall anyone saying if LAN play works properly for higher difficulties. If I recall correctly, when you are refused the Nightmare game, it should say that you need to be at least level 20. The issue is that you are treated as a level 1 warrior, not whatever level and class you actually are.

Just a heads up, I reported the issue to blizzard and the rep told me to post a bug report on their forums so if you're having the same issue as I am please add to the topic over here us(dot)battle(dot)net/forums/en/bnet/topic/20771127507 (remove the (dot)s and add a . as needed)

If we get enough people on them about it they might actually do something otherwise I see bnet never working the way it should and thats no fun.

Edit: a couple of snippets of the convo with the rep

RITORACK 20:57:53
Hrmm, tricky situation. Truthfully, we don't have any tools to check in-game issues for Diablo I :X

RITORACK 20:59:10
Aye, the updated version of the game was created to be fairly self sufficient, so any in-game issues like this should be reported as a bug instead so it goes to the developers.

Then it's a good thing this isn't an in-game issue, but an in-chat one. ;)

To be a bit more serious - if I were assigned to work on this, my first step would be to try to determine whether (a) the client is incorrectly sending level 1/warrior to the server, which then faithfully parrots back the bad data or (b) the client sends your true level/class, and the server wrongly sends out level 1/warrior instead of the real data. This will tell the developer whether to fix the client code or the server code. The easiest way to test this, assuming they didn't rewrite their battle.net chat protocol, would be to find someone who has Diablo from an original disc (patched up to v1.09) and have that person modify their registry to join the new "Global" battle.net server. We know that disc Diablo did the right thing with regard to statistics in chat, so if that person is also impacted, that says the server is broken. If that person does not experience the bug, then the new GOG Diablo client is broken. (We could also try to find/host a private battle.net like server, or monitor the traffic sent between the client and server, but both of those are much more advanced topics and might cross into the areas Blizzard doesn't want people exploring. Differential analysis of the disc Diablo client should be perfectly within the license agreements though.)

That tells which component needs attention. Going deeper would be a task for a Blizzard developer, since they should (but apparently don't :)) have the tools to trace the bad component to see where it first goes wrong.
This is just upholding tradition. Diablo has always had embarassingly obvious bugs that you wonder how they were missed. :) From memory, there are the bosses that never appear because their dlvl is wrong; the unique items that cannot be dropped due to qlvl collision; the quirk that King's has better statistics than Champion's, but the game considers Champion's to be a better prefix; the numerous ways that the game can be remotely crashed by a cheating player. If we look also at the bugs that were fixed post-release, but made it past internal testing, I like the one that you could cause the red Lazarus portal to close prematurely and the one that you could freeze your game by touching a Hidden Shrine while there were no items for it to change.