Laravel 7.x hosting problem in shared host

I am trying to host a laravel project on a shared host. but my project is not running. please check the image

I have checked in error log. and it returns the following error message

[25-Apr-2020 14:02:09 UTC] PHP Fatal error: Interface 'JsonSerializable' not found in /home/devcornx/public_html/aweerapp/vendor/laravel/framework/src/Illuminate/Support/Enumerable.php on line 11

My server php version is 7.4. and json is enabled. please see the following image enter image description here

Please, Help me. i am totally messed up with this.