We are using Bluemap(ver3.7) before and there is a button can check player count.

but when we update Bluemap to version 3.13,The button disappeared.

We've tried deleted the whole webroot folder,but it wont work.

If that button is missing, then there is something wrong with your setup.
GitHub is the wrong place for support. Please visit our discord, there we can help you find the issue :)