i had the same error , with my old Hosting , i used to get the error 500 but after clik refresh the error disaperaed. i do know exactly wht cuz it but Now i'm with new hosting and i dont have the error anymore..

if you updating protector from 2.3.3 try remove all old files and upload fresh .. it might help if you try first on local machine and see if u get the error.

Good luck