Hi @koumoutsos,
Let’s treat that separately, as it’s different than the issues in this post – that’ll help keep the forum organized as a resource for others. I’d suggest reviewing existing postings with that error message (e.g. Upgrade failed 2.4.7-1/2.4.8-1 --> 3.0.0), and if those don’t help, post a new one with details on what you’ve tried so far.
Thanks,
Alec Smecher
Public Knowledge Project Team