Unfortunately, i'm not a "software pro" and the BitcoinCore is not able to open anymore for the last 2 or 3 weeks.
I've got this message :
"a fatal error occurred, see debug.log for details" .
In this file i have very often that :
AddPortMapping(8333, 8333, XXX.XXX.X.XXX) failed with code 718 (ConflictInMappingEntry)
Any advise ??
Just in case, do you see any other error / warning message? If you're not sure, you could try share content of debug.log either here or website such as Pastebin.