I accidentally solved it by myself... for some reason I got myself a 5.6.2 DragonBones (but the installer change logs states that 5.6.2 returns to 5.6.0) so it says on my welcome page that it's 5.6. Anyway, I can save now without needing to login at all.
What I did was download the older versions till I got the latest that didn't need to login, I was already at version 5.2 (after trying versions starting from 5.0). When I was installing 5.2 a popup appeared saying that there was a newer updated version of DragonBones (5.6.2) available. I had no idea how I got that popup, it had change logs and the most recent update was last 2018-10-something. Of course I took the opportunity, installed that and thank god it's fixed.
Sharing what happened to me here in case it works for others... since I really can't find other answers for my problem in the internet. DB hasn't updated for 2 years, and posts are outdated. It's such a shame really.
Update: Did it for my other laptop and it still worked. Here's a screenshot.