Powerline AV500 won't even try to pair

Hi All,

I've had a poweline network installed for several years, all good, all happy.

XAV5201 to router.

XAV5201 to PC.

XAV1301v2 to media streaming device #1

XAV1301v2 to media streaming device #2

So 4 in total.

I just bought a TPlink TL-WPA4220 to add to allow wifi in a distant room

and tried to pair with the XAV5201 on the router but pressing the pairing (security)

button on the XAV5201 has no effect, I expected the led to start blinking but it doesn't.

The new TPlink device is irrevelent at this point since it's not even plugged in, but why won't

the XAV5201 even go into pairing mode?

If I press the security button for a long time the powerline led seems to flash red once briefly

but nothing changes - it's still not in pairing mode, and all the other plugs still work.

I don't want to do a factory reset unless it's an absolute last resort since some of the

plugs are in impossible to reach places and it would be a major undertaking to get to them

in order to re-pair them.

Any thoughts appreciated.

Steve