problem on WHMCS

[specialrdp]

Hello today i just want to upgrade my WHMCS Panel.but its not updated or maybe its got failed

now i am not able to access WHMCS panel just getting error like

is currently unable to handle this request.

HTTP ERROR 500

HTTP ERROR 500

 

and when i checked error log i found something like this

0 /home/urmit9965/public_html/billing/init.php(0): unknown()
1 /home/urmit9965/public_html/billing/init.php(0): gracefulCoreRequiredFileInclude('/vendor/autoloa...')
2 /home/urmit9965/public_html/billing/register.php(0): unknown()
3

thrown in /home/urmit9965/public_html/billing/vendor/autoload.php on line 7
[22-Jun-2018 08:09:53 UTC] PHP Fatal error: Uncaught Error: Class 'ComposerAutoloaderInit83a7c393734f640a50aba6541ba5' not found in /home/urmit9965/public_html/billing/vendor/autoload.php:7
Stack trace:
0 /home/urmit9965/public_html/billing/init.php(0): unknown()
1 /home/urmit9965/public_html/billing/init.php(0): gracefulCoreRequiredFileInclude('/vendor/autoloa...')
2 /home/urmit9965/public_html/billing/cart.php(0): unknown()
3

thrown in /home/urmit9965/public_html/billing/vendor/autoload.php on line 7

 

so kindly please help me how can i fix it?

even i restore my old mysql whmcs file still not opening i don't know whats going on?and then i replaced my old version patch still not opening panel and nothing

 

please help me

 

Regards,