I haven't found a way to contact Roku about developer issues like this one. I think we may be out of ideas on fixing my problem but I don't know how to contact them to report this. There are no error messages anywhere. The Feed Status says I have 784 items. I don't know where else to look for a problem.
The only thing I can think of is that I'm exceeding some limits somewhere (silently), but that should give some error. Bah.