Cisco 7945G not registering after firmware update

I need help.

Just upgraded a 7945G phone from SIP firmware 8.x version to 9.x version.
Phone was working fine with SIP version 8.x but not registering after firmware upgrade. Remains in continuous ''Registering" loop mode. I cant even see the phone trying to register on Asterisk CLI.

Any idea as to what might be the problem?

Thnks

Nope. And this (kab00m.ru/lib/node/17) says it’s a no-go. Try rolling back to 8.x

Cheers.