@philb452 - first things first, what firmware version is running on the hub? You can establish this by navigating to the Advanced > Technical log section of the Hub Manager.
Try taking things completely back to basics. Factory reset both the hub and extender by inserting something into the pinhole at the rear of each device and holding for a good 10 seconds or so. Once the hub is back up, try connecting the extender using an Ethernet cable. Allow the extender to pair (solid aqua) and leave it connected via Ethernet for a few hours. This hopefully allows time for the extender to download any software updates, when it does this the pairing tends to drop and the extender lights do unexpected things before eventually repairing.
Hopefully the extender now shows in the Hub Manager. Check that it is running the same/similar firmware to what is installed on the hub. Navigate to Advanced > Wireless > Extenders and highlight the extender (assuming you can see it!) to check this.
Only then would I try removing the Ethernet cable but don't relocate the extender just yet. Wait to see if it re-pairs (solid aqua) over Wi-Fi. Assuming it does, you can then relocate it. Note, do not place the extender in your home office if the signal is poor there. The extender needs to be in a location where the signal is good, in order to push a healthy connection further into the property. The Pro extenders also use 6GHz to communicate with the hub and whilst faster, it doesn't reach as far and doesn't like obstructions. If you're trying to physically locate it in an area where a (presumably 5GHz) signal is bad, then you're going to have a rough time of things.
Good luck!
