Can't get XR500 into AP Mode

[Toxic Smoggie]

Hi All

 

I'm trying to get my XR500 into AP Mode as I'm wanting it to act like a wireless AP in the office (little front bedroom), I've reset it back to factory setting went through the config but when I go to Settings > Router Mode > select AP Mode then hit Apply I'm getting the message "400 Bad Request This server does not support the operation requested by your client."

Currently I have the R3 as my primary router and have a powerline from downstairs to the XR500, I've unchecked Use Router as DHCP Server in Lan, I'm not sure what else I need to do to get into AP Mode

[Toxic Smoggie]

All sorted somehow