Hello TadasJunknevicius,
The “PackagingResults:Error: Error Unknown Cook Failure” message means that there was an error that occurred that caused the packaging attempt to fail but doesn’t give any information on what the actual error is. Whenever you see this error, you need to use the Find feature (ctrl+f) to find the word “Error” and “Warning” throughout the log to find out what the actual problem is. Unfortunately it doesn’t seem that any of the messages posted here point to what the actual issue is. Can you please upload the full log file from this packaging attempt? It can be found in the project’s directory under Saved/Logs.