Hi @xaid_warraich,
Are you able to check your PHP error log? Usually when you see errors of this nature (e.g. HTTP 500), it is best to check your PHP error log, as it provides error messages that often point to what is occurring in your instance that could be leading to such issues. For some advice on how to access your PHP error logs, see here: How do I find my PHP error log?
-Roger
PKP Team