Some users have reported problems connecting to their UniFi controllers using PCs and Laptops.

The error is either “No network available”, or the connection drops / disconnects occasionally.

We found this article which might be useful in troubleshooting the issue:

https://community.ui.com/questions/Cant-connect-to-wifi-for-some-PCs-and-laptop/57dbe4ce-3051-40ba-b4a4-3ae59978997f

If you experience this issue, try this fix:

Make sure Auto-Optimize Network and High Performance Devices are disabled.

Settings > Site > Auto-Optimize Network

Settings > Wireless Networks > SSID > Advanced Options > High Performance Devices

Also, could you post your system config?

Settings > Maintenance > Support Info > Show System Config