Video Assist Not Monitoring

I am shooting with a BM URSA Mini Pro and a 5" Video Assist,
cabled via SDI out from the rear side of the camera through a BMD SDI to HDMI box and then via HDMI into the Video Assist.
The converter box is powered, the Video Assist turns on fine, but I am not getting a signal to the camera.
(Yes, I'd used an SDI cable exclusively, but I don't have one that fits the inputs on the Video Assist).
Please feel free to tell me I'm daft, but I am shooting on Wednesday and would LOVE to solve this

Thanks for your help.

FYI - the camera is set to film mode, 23.98, ProRes 4:2:2 and the Video Assist is set to ProRes same frame rate...

Is the rear output on the UMP set to HD or UHD? While the Video Assist will accept a UHD signal the SDI to HDMI box might not.

My first question, why are you converting the UM camera output to HDMI? The Video Assist has a SDI input, which takes HD and UHD signals. Roger is correct, that the UM rear SDI output needs to be set to either HD or UHD, but the VA only works with UHD signals via its SDI input. The HDMI input is limited to SD and HD only.
Cheers

the VA only works with UHD signals via its SDI input

True! I forgot about that.

Yes, the HDMI interface on the VA is an older lower bandwidth chip, that only goes to HD, from what I gather, ot it is just limited to HD. Same with the Micro Studio Camera, UHD is via SDI only.
Cheers