Thanks for your suggestion. I spent on this problem a few days now and here is most of the things I have tried to do so far:
Delete all traces of MU online client and download fresh one
Added exception for main.exe and launcher.exe to antivirus and firewall
Tried all different compatibility modes
Downloaded Malware bytes, CCleaner, Registry cleaner to get rid of any viruses, rootkits etc
Tried to run client without VPN, with my paid version of Express VPN and with free Proton VPN [the only one that actually works for me]
Created another user profile on Windows and tried to run the second client there
All the suggestions from text file in game folder !!!!ATTENTION IF GAME IS NOT WORKING
Used sandbox
Reinstalled Visual C++
Rolled back windows updates with which the game run ok before
Updated graphic card
Flushed DNS and reset network
Reset Windows with keeping my settings
And probably few more things I cant remember atm. My only guess I have left is that around that time I installed ReShade for NFS which online game servers can flag it as cheating. I uninstalled ReShade the proper way, deleted the game and went through registry to get any mention deleted but its not easy. Right now Im in the process of reinstalling the whole Windows and if that doesnt work I'll just stop playing, cant be bothered anymore because as you say, some people play 8 chars and I cant run 2 instances of the client at the same time.