SSRS SubReport Error

In need of some Tessitura friends who have spent WAY more time in SSRS reports than I...

I've copied and altered the canned Performance Seating Book report to fit some additional needs and I have it 97% working in TEST the way we want...BUT for whatever reason, it isn't running the subreport that is supposed to show the parameters used. What am I missing?

Here's the error:

Here are my subreport details:

Thanks in advance!