HP switch & a Cisco 7941 phone

Check out the MDI-X settings on the HP switch and see if they are turned on or off.
You may need a crossover cable to make it work correctly.

I tried a crossover cable but thanks for the suggestion.

All the firmware up to date on the devices?
Looks like you may have a Cisco proprietary software issue.(which would come as no surprise).

The cisco switch uses auto vlan assignment based on MAC address of device. You gave to make sure your hp switch is similarly configure to auto assign the phone to a voice vlan which is how the Cisco phone will get an ip assigned ........

the other option, you have to assign the port to the voice vlan on the hp switch.

The phone is using cdp/lldp (I think I got the alphabet ... Close) to locate the cucm with which to register after tftp boot, config load...

Check the settings of this phone dealing with ip and compare it to the functioning Cisco sw connected phone.

To avoid this situation, take the time to configure this hp switch to get this Cisco phone working at which point you would gave the info should another location have to rely on a hp switch to connect a Cisco phone.
If you give up by ......
Like the last time you will likely end up in this position as you have before.

Here is a discussion from long ago that deals with a similar scenario, you can get an idea from that and apply it to the devices you have ro address the Cisco phone ..

https://supportforums.cisco.com/discussion/10561101/hp-procurve-switches-and-cisco-ip-phones

To clear it up a bit, this is a physical problem.  The phone doesn't use auto-VLAN assignment based on MAC.  It uses CDP on a Cisco switch to get its VLAN info if the voice VLAN is configured on the switch.  It uses TFTP to get its config and that tells it how to locate the CM.  When you use a HP switch you should use LLDP and configure the voice VLAN with the "voice" command, like this:

vlan 10
 voice
 tagged trk1
 untagged 1-24

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Anyway, how are you powering the phone?  Are you using PoE from the switch or an injector or PSU?
What version of code are you running on the phones?  Do they support LLDP?

I'm using POE to power the phone. I'll have to get back to you with the code version. They are old (2008 - 2009?) and haven not been updated.

Cdp if not mistaken is a discovery protocol, if the HP does not auto tag the phone as being part of the voice vlan, the broadcasts the phone does will be locked on the vlan to which the switch port defaults at which point no tftp info, no config download no registration will occur without manually configuring the network settings of the phone including the ip of cucm with which it has to register.

I have the voice vlan set and assigned to the switch port. LLDP is enabled on the switch and the phone. I'm going to spend a little more time tomorrow looking through my switch settings to see if i have missed anything. Thanks for all the ideas. Keep them coming.

Check the feed from ... Is it defined as a trunk? Or part of a specific vlan on the switch?

CDP is a discovery protocol in that devices exchange info using it. Phones don't get any config via CDP though. The HP switch won't auto tag the phone; just packets to it.

If the firmware on the phones is old I'd suggest using a version that supports LLDP.

Ah! Wow yes you're right. I forgot all about this. Prestandard PoE swaps blues with browns, so a little different to how you have it. Well done working it out.

Lots of research and trial and error