Hello @Sandeep Shah
mysite.com is the root domain, this is also known as an "APEX" domain.
Unfortunately root domain support is not available during preview.
https://learn.microsoft.com/en-us/azure/static-web-apps/custom-domain#configure-a-root-domain
You can make a workaround for your mysite.com domain, create a CNAME at your domain provider, that will point your mysite.com to www.mysite.com
https://burkeholland.github.io/posts/static-app-root-domain/