Resolve PBX Desk Phone Registration

I recently migrated our system to a new PBX and I’m running into inconsistent desk-phone registration. Some handsets pop online right away, others refuse to register at all. The odd part is that every... (Budget: $30 - $250 USD, Jobs: Asterisk PBX, Firewall, Linux, Network Administration, PHP, SIP, Telecommunications Engineering, VoIP)