Login to your CloudFlare account via this link, then follow below steps :
From website options, select “network” as shown in the below picture:
Activate the option “IPv6 Compatibility”:
This action can be fulfilled as well using the Cpanel by following the below:
Press the button “cloudflare performance”, as shown below:
Press “setting”:
Change “Automatic IPv6” from Off to Full as shown in the below picture: