WOW I just spent ages messing around with this phone! Couldn't get it to register direct with Voicehost at all.
Looks like Voicehost have been updating and making changes to their service. In the end I had to set SIP URI: xxxxx*
xxx@sip.voicehost.co.uk in order to get it registered. (Will have to update the guide)
I got the same result as you, BLF is not working. I am sure it used to with these phones!
I had the Panasonic set as Extension 201 and a OBIHAI 1032 as Extension 202... Make a call on the Panasonic the BLF on the OBi1032 works just fine, make a call on the OBi1032 and the Panasonic phone BLF fails to operate. Clearly an issue of Voicehost not supporting or no longer supporting BLF on the Panasonic phones.