Found another potential solution after getting desperate when all other posted solutions didn’t work.
I had two plugins with this issue while other plugins worked just fine.
I simply spammed the install button for those plugins, switching between the two and trying different versions available for all the UE versions I have installed.
After around 8 failed attempts, it just randomly worked. Now I can install any version of the plugins without any issues.
Maybe just spamming the install button itself already works and it might not be necessary to do this whole switching versions and plugins thing.
Though I don’t think it made a difference, I should add that I did all of this with an emptied VaultCache, running as Administrator, and after having applied all the solutions listed above.
Solution is Keep everything and open launcher go to UE section → Library → Scroll down to fab library wait for syncing is done and you can install your stuff without any errors
Doing everything mentioned above like emptying folders + killing on task manager + running as administator + installing from the Unreal Engine section / Library instead of FAB worked for me
You’re right. This is the fundamental reason. I’ve tried all the methods, but they didn’t work. Because I have a lot of assets, I need to wait for a few minutes before the refresh is complete, and then I can use the plugin to download. It has been bothering me for a whole day.