Instant tracking no longer working off prev. working forked version

Hi -

I’ve got an instant tracking build that previously worked on my phone. That version still publishes fine off the 1.57 engine.
This is that version.

I’ve forked this version and republished a build and the camera feed isn’t showing now. No idea what as they’re both the same.

any clues ? I’m baffled - is this probably a zapworks issue isn’t it ?