Hi almost at the end of the game. I just finished the quest for the Temple but there is no option to go to the island. On top of that the people at the temple won't even speak to me anymore. No option comes up with the sea captains and Tech is still at his ship.Playing a good alined character with the performance mods. Any idea what the issue is and how I can fix it?

If you speak to any of the Sea Captains, you can ask them about Thanatos. They'll tell you only those crazy guys in Blackroot know about that.

Not sure how much of a spoiler you want, so I'll leave it at that.

Played the game many times you don't have to worry about spoilers. Problem is the option is not coming up. The quest to find out about Nasradin is still active and this is after all the temple quests are finished meaning no way to find out about Thanatos.

Even if you can't talk to Teach, you still may be able to bypass the issue. Travel to Stringy Pete's cove anyway, and see if he still shows up. If he does, his ship should still list Thanatos as one of the options.

Likewise, buying your own ship at this point should unlock Thanatos. If it doesn't, then the real problem becomes how to close the Panarii temple quest in such as way as to trip the right flag. And that may be down to a glitch, in which case your best bet is an earlier save.

I think if you pickpocket Gunther Willhelm's note about discrepancies in the Archaeon, it will initiate all the Thanatos dialogue at Black Root as far as I remember. Useful if you've burnt out all your other options, as you can just spend a fate point.

A fun fact is you can be evil and still do this when you side with the dark elves, leading to a unique face off at the Ring of Brodgar if you play both sides off against each other - terra-arcanum.com knowledge for the win.