Ahhhg, I thought I had it, but no.
I cleanup all the errors in the terrain.
I do a check. It says all good. Ready for upload.
I run ahupload. It looks like it's going well but just stops at "Building complete." It doesn't appear to start any upload.
I had checked "Upload terrain to host".
Is this maybe because it has custom objects?
I only did it about a billion times. Sooooo painful.