NGINX Proxy manager UI not working

[VE3TRU]

I have installed NGIX Proxy manager Via Docker and I cant open the UI
It says

Firefox can’t establish a connection to the server at xxx.xxx.x.x:81.

The site could be temporarily unavailable or too busy. Try again in a few moments.
If you are unable to load any pages, check your computer’s network connection.
If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the web.

I tried clearing the cash and still nothing

not sure what to do.