Sorry for long time with no answer, but I have solution - a little bit funny. When I clicked "Activate product" ESET Protect was trying activate FDE license with ESET Endpoint Security license and there was no change of it working... Solution: when you creating activation task from Computer details view, you should be aware which type of license you will use to do this task - automatically ESET choosing first available license, in my case it was wrong type.
So, It's all ok, now I know I should choose which license I need to use. GUI in this case was so illegible. I could not do it without your hint about debug mode in ESET Logs, thank you so much!