Dear Team, I have Upgraded our sugar CRM 11.03 to 12.00 & we are Getting CRM after login screen ( HTTP: 500 Internal Server Error Unknown error. ) Please help what can i do for this issue

Dear Helper Team, I am using SugarCRM 9.0x Enterprise and want to update Latest 11.0x Ep How we can update please guide me for update to latest version. We have 4 Instance 1-Developer instance (Development coding purpose only ) 2-UAT Instance…