For those using a 32-bit OS, please delete the BE Service folder ("C:\Program Files\Common Files\BattlEye") and then manually update your BEService.exe from here: THAT LINK. This should resolve your issue.
A fix for Windows 10 will follow later.
Did that and error persists "Windows Test-Signing Mode Not Supported"
Same problem. And, although I knew Test-Signing was off, immediately after it happened I threw out the command to turn Test-Signing off and still was presented the same error; " Windows Test-Signing Mode Not Supported"
Can't Launch ArmA 2 OA/BattlEye: Windows Test-Signing Mode Not Supported
in ARMA 2 & OA - TROUBLESHOOTING
Posted
Did that and error persists "Windows Test-Signing Mode Not Supported"