Hi Jon
I had the same problem, some 2 months ago. I described it in this thread: https://community.pix4d.com/t/4664-Capture-App-with-DJI-Inspire-Pro-Exchange-of-Experience#gsc.tab=0
The problem in my case was the usage of the mode-switch. In order to allow the mission to be upladed while on the ground, I switched to “F” and then back to “P”, before liftoff. That wasn’t a good idea. When I took off in “P” without prior switching to “F” and then - while hovering - switched to “F” and uplaoded the mission, it worked.
However, I had quite some problems with my I1 Pro / X5 with Pix4Dcapture. I finally gave up because Pix4D claimed that they wait for a new API from DJI…
But I’m very much interested in any news in respect to the X5.