On our current PSTN land-line, we have a Panasonic KX-TCD540NZM base station, and I use two portable handsets one of Type KX-TCA150AZV and the other KX-TCA154AZM.
I tried to pair each of these with the Genius base station, but initially couldn't do so.

However, I could successfully pair the Genius handset with the Panasonic base station!

Then, I deleted the pairing association between the Genius handset and the Genius basestation, and paired one of the Panasonic handsets successfully. Yay, at least they are compatible!

But I then couldn't pair the Genius handset with the Genius basestation without removing the pairing with the Panasonic first. Both Panasonics pair with the Genius on their own.

In the Genius setup menu, it seems to show that all 3 handsets are paired? But only 1 works?
Question: Is there something wrong with what I am doing? i.e do I need to wait until my voice service is up and running before I will get the Genius basestation to work with more than one handset, or is this a limitation of the product?
Anyone else able to shed any light? I am happy to trial more options.
I'm sure I'll get a working arrangement out of this, but just don't see why the Genius will only allow one handset at the moment? Maybe there's a software set limit, since the product only seems to ship with one handset? But then, why does the setup page seem to allow for 4 handsets?