On Procurve switches, all you have to do is,
lldp enable
vlan 2 voice vlan
Sadly, the 1920 isn't procurve.
If you have a look at the 1920 CFG guide on p160 you can see it says you have to do 3 things:
- configure Voice VLAN globally
- configure voice VLAN on ports
- add your phones OUID (that's their MAC address prefix)
That last step might be the bit you are missing:
Network > Voice vlan > OUID add
(You can see your MAC address prefix on the back of your phones: 0800 0F......)