Having the same problem. These are the "solutions" I have tried:
Clean install, asi loader, empty mods folder, RPH
Existing back-up, asi loader, empty mods folder, RPH
Clean install, RPH
Existing back-up, RPH
Allow everyting for RPH in firewall
Fullscreen launch
Force windowed mode
launch game frome RPH.exe
Launch RPH after game launch
The GTAVLauncher.exe keeps nagging that the game should be started from Steam. Don't know if that is giving the problem. On the other hand, this error first occured when Windows10 was updated to version 1903 a few days ago (maybe RPH needs to be updated to work with this Windows version. Just guessing).
I'm not getting an error log from RPH to upload.
EDIT:
Just tried again with elevated privilages, still no luck.
I did notice that in the root game folder, there is a file called 'rphhs'. It's file extension is "bestand" (wich is Dutch for "file") So there are a few questions that popped-up to me:
does this file have anything to do with RPH at all
if yes, can I force the file extension,
if #2 applies, what should that extension be
Hope someone knows something😅
EDIT2:
Added RPH in AntiVirus to the trusted list, still no luck
Also added the Whole GTAV folder as an exclusion to check for the AV. Also nothing
Adding RAGEPluginHook.exe as trusted also didn't work
EDIT3:
Deleted my anti-virus (KasperskyLab) and somehow it works again