Laravel 5.3 on Ubuntu 18.04, Post requests are not working

I have a Laravel(V5.3) application On Ubuntu 18.04. All routes work well on my localhost (windows) but in the live server the POST requests returns

"Whoops, looks like something went wrong."

If you submit, it will return the above message.

I have following values in .env

APP_ENV=local
APP_DEBUG=true
APP_LOG_LEVEL=debug  

I cleared route, config, cache. I tried composer dumpautoload

I checked laravel.log - No errors. I checked the PHP error file - No errors

via Chebli Mohamed