Why can't I register a plantronics c351n dect headset with my studio 1100 base? Both are compatible with GAP standard. I've deleted all but one handset so as to free up a slot for a second gap device but doesn't work even after reseting base as per instructions from this site. I like the studio 1100 and don't want to change my phone just to get the headset working.

Finbarr, January 2009