Logs with errors are not present, except for "error.log", which is created at startup. I just can't understand why, why does the program close if it works? It even can to download files, if they are small.

After blocking access to the address 5.9.113.110 (cdn0.appwork.org) the problem is gone.

It's like here - https://board.jdownloader.org/showthread.php?t=77544

Is blocking a good idea? Does that not stop it from updating correctly?

See the thread noted - seems to be virus/malware apps causing the problem. Easy enough to turn them off for one minute and just update.

[Jiaz]

The issue got fixed. I will post explanation in other post

[Jiaz]

sorry for the inconvenience