It is active (as in I'm responsing) only due to the recent release. I usually don't devote my weekends to work. I'll be sure to reply to all new threads on Steam forums and mails on Monday.

As to your question - every major patch what you've described indeed happens, not entirely however. You can go to earlier missions, because the progress itself is saved. Everything you unlocked, all the chapters you finished are properly saved. What is no longer possible to load is the actual state of the map. So a save 15 minutes into a map will be lost, but all you have to do is just replay those 15 minutes after the patch. All previous maps are properly marked as finished.

I know this is far from ideal. I want you to know however, that this is a very difficult technical problem to solve. Many titles have a similar mechanic and I could list those titles, some very well known ones, if you wish. At the release, we've allowed such saves to be loaded. Turned out it crashes the game or completely breaks the mission in vast majority of cases (around 90%). We've researched the topic and just as many other developers, decided that a message informing of the issues is better, than a crashing or broken game. It happens because the save game's data no longer matches the newer version of the game. It's like reading a corrupted file.

We've already noted this as one of the known issues with a desire to improve on that solution for the future titles. Unfortunately, it's going to stay that way for Ancestors Legacy. This most probably is not what you'd like to read, but I hope you prefer a detailed explanation and truth, rather than alternatives.

No need to use our forum, this is ok. I only meant that I was responding here on weekend due to release. I will be a regular visitor here from now ;)

None of the save games can be read, you are correct. You can however play all the previous missions again, they are unlocked, and you can continue your progress by starting the last unlocked chapter again.