Vincent, I´m having the same issue, and have done everything listed in all forum posts I could find, and still, cannot download anything from quixel, sketchfab and twinmotion cloud libraries. I have two twinmotion versions installed, 2023 (paid version) and 2024.1. In both cases, I did not succeed in downloading anything whatsoever; in fact, the 2023 (paid version) actually crashes when I try using HDRI backdrop. I really need a solution, because it´s impacting severely my workflow.