[AP not working with Capture One Pro . . .]

Can you try to flatten the layers in Affinity hit Save and check if it updates the TIFF on Capture One?

I don't have Capture One so i'm just guessing here.

 

I tested with a single layer in Affinity, so nothing to flatten. It just refuses to load in Capture One.

[AP not working with Capture One Pro . . .]

I have this same problem with Affinity Photo 1.3.5 as well, with C1 8.2.3. Does anyone have it working?