I m having the same problem about the same time after the launched of the NEW FAB.
All my purchased FAB libraries are now unable to be installed or add to any of my projects/Unreal engines.
All our game development projects had been suspended or prosponsed due to this serious issue.
Urgently need assistant from the Unreal Technical Supports. Thank you.
Same issue. Nearly none of my old fab plugins are able to be added to projects nor are projects able to be created from the Epic Games Launcher, preventing use of several important plugins in research projects before integration into our main title.