Cs cart php version upgrade issue

we are trying to upgrade cscart version .
as we are upgrading it askes us to upgrade php version to 7.1
then we change the php version to 7.1
but as soon we upgrade the cscart stops working and shows this page isnt working
so we are unable to upgrade
please help us let me know if anything could be done



Please check the error in the error logs of your server and copy/paste it here.

Do you see empty white page or any error message?