I've come accross this old error recently, but none of the existing solutions have worked.
I have tried:
Reinstalling GTA & MTA
Trying the latest Nightly
Running both GTA & MTA as Admin
Running in Compatibitlity Mode
Created a new Windows User Account
Replacing my deatmatch folder
Replacing only client.dll
And none of the above have worked.
I am running the latest MTA stable version now, in Windows 10. Antivirus is installed and enabled, and before posting this I've also ran an analysis on my computer to ensure no virus is causing this issue.
As requested by @ccw I am posting this here.
Any tips at all will be appreciated!