@Dhwuud 

Enable the guest network and do not set a password, see if the iPad connects. If it does, forget the guest network and configure a simple password and see if the iPad can connect to that.

If you are running the latest firmware 1.2.5 or 1.0.5, tap on the password for the wireless setting of the main network and try changing the security to AES.

@Tony 

the change of password after taking password away on guest network worked on my X20.  Only issue I had was on an iPad3--it initially worked fine.

@Dhwuud make sure you do not have WPA3 enabled.  The iPad still does not support this latest security protocol.  You can still use the WPA2 with AES setting on the router, and that should work since it is compatible with the iPad

Dhwuud wrote

I have one device that will not connect to my x60. iPad gives me "unable to join...". Password is correct, beamforming turned off, fast roaming turned off. I have reset the router. I have also reset network settings on the device. 
 

the iPad will connect to the old router, so likely not purely a device issue. 
 

this is driving me crazy....any advice?

Dhwuud wrote

I have one device that will not connect to my x60. iPad gives me "unable to join...". Password is correct, beamforming turned off, fast roaming turned off. I have reset the router. I have also reset network settings on the device. 
 

the iPad will connect to the old router, so likely not purely a device issue. 
 

this is driving me crazy....any advice?