How to connect more than 20 devices to ATT fiber router?

This is an internet question and you have posted it in wireless. Wireless is cell phones and such wrong department

let's move this ...

In the device's web interface, select the wireless settings, click on the Advanced Settings link and look for a limit to change there (per radio frequency maybe).

@thechef1 

I don’t recall ever seeing that option, doesn’t mean it wasn’t there all along.  

The default for the two main radios is 80.  The guest WiFi setting default is 10.