I hate to be a bother for something so old but I have a KX-TA624 that I'd like to get hooked up to a KX-TVS50. Problem is that the ROM on both TA624 boxes that I have are outdated. The one we are using right now stand at Y501Y. I purchased a used box on ebay that was a circle 5 unit but that has older software on it than our old one (Y451G). Would anyone happen to know where I could find a ROM upgrade for this unit or if it's still possible to even hook this VPS up? I really appreciate any help I can receive. Thank you!

I should mention I did do a search of this website and found numerous posts regarding the same issue but none really had any fixes or workarounds. I'm hoping that's not a sign of these ROM upgrades being impossible to find. =) But I fear I'm wrong.

Are you using a four wire connection to the voicemail ports and have the voicemail ports set to APT?
I did find this in the TS50 manual
KX-TA624 that can use APT Integration is:
• KX-TA624 Version Y581A or higher

If you look in the installation manual of the KX-TA624 on page 4-42 setting up APT is explained for the TVS-50 and TVS-80. using a APT "Proprietary" Panasonic phone set.

The Installation Manual I am looking at is from 1999 PSQX1424VA KW0698KM7021APC

According to this online data at Telecomwarehouse the KX-TVA50 IS compatible with the KX-TA624.

Panasonic KX-TVA50 Voice Processing System (KX-TVA50)