Another cursed bug has been added to the list at FAB. After the terrible errors in the payment method, I can never install the plugin after purchase. Nothing I’ve tried has worked. You haven’t been able to fix these problems for years. ■■■■ it.
ERROR MESSAGE: Error Code IS-EO-Lnc-BldInfo:Http-403
Same. There’s another thread: Error Code IS-EO-Lnc-BldInfo:Http-403 - General / Issues & Bug Reporting (Fab) - Epic Developer Community Forums
Absolutely no plugins are installed… Absolutely not a single plugin is installed… Is this a joke?
Good news, fellow sufferers: I accidentally found the cause (in my case, at least).
Run the Epic Games Launcher as administrator. That’s the whole fix. A plugin installer that worked flawlessly a week ago now can’t write a single file to disk unless you hand over the keys to your entire operating system.
I don’t know what the brilliant minds shipped in the last update, but apparently installing a plugin now demands the same clearance as wiping your drive. His Majesty does not simply download, His Majesty must be granted dominion.
You’re welcome. Try not to enjoy the unrivaled quality too much.
This didn’t work for me.
Hey guys the Run as administrator solution didn’t work for me but I found out that if you can get the plugin from the developer ie… from their discord or from their website and extract the files into your projects local “Plugins” folder whether you need to create a new one or not put it in there (putting plugins in this folder is also how you are able to edit the source code of the plugins). Then just launch your project and enable the plugin under the “Local” tab in plugins restart it and you’re set! Try asking the developer of the plugin to give it to you if it’s not directly available. Good luck 
Thanks so much for flagging, the team is checking into this.