Thank you for the quick response Exile360,
Sadly none of the steps above solved my problem.
After trying all the solutions you gave me, i uninstalled mbar 3.4.5.x and installed version 18.104.22.1683.
It gave me an error during installation (runtime error 0x5), but surprisingly after the installation, malwarebytes initiated. i executed a verification and no threats were found.
The service "Malwarebytes Service" keeps not showing up on Services.msc, so I think the problem may be on the Windows O.S.
Anyway, thank you very much for your help.