P Series Static Route

Hi Have a P Series that sits on a network that has phones on 3 different IP Ranges.

Pabx 10.0.0.250 Phones on this IP range register.

Phones that are not registering are;

10.27.1.0/24

10.27.2.0/24

10.27.209.0/24

We have just moved them off a Grandstream where they worked onto a Yeatstar P 560 where they are not registering.

i have added all onto the static routes and it still doesn't work.