Downgrade Firmware

I've recently purchased a SIP video intercom that I am using with the VP530s. I've been though 3 days of support calls with the intercom company we have combed though every setting. They have the exact same phone, and intercom as I do with the same network setup. However, the video coming from the intercom is black when the intercom calls, but when the VP530 calls, video is received from the intercom.

The only difference between my setup and their setup is my firmware on my VP530s is newer. They have 23.70.0.40. I have 23.70.0.41.

Can I please have a link to downgrade my firmware to see if that is the trouble?

Thanks,
Brad