David: Thanks for your interest and willingness to help. I cannot understand it, but today all is working well. I am absolutely sure that the student had the right permissions and that dates and times were set for open submissions. I really don't believed I was tripped up with military time This might have been related to whatever problem I was also having getting ratings to work on forum posts. I thought perhaps that the custom scale I had developed was inadequate in some unknown respect.
Last night I switched the rating scale to the standard numerical scale without the descriptive detail I'd wanted my students to receive, and the forum rating started working. I made the same switch in rating scales for the workshop and the submit button appeared for students to do their work. Therefore my suspicion of error in the rating scale I was using doesn't seem to have been the problem. I'd cleared cache and was working in designer mode with the standard theme just in case. It sure beats me what was going on.
Sorry to be long in posting this update. I really wanted to get five sample students all the way through the workshop process, and they did so.. and to the gradebook with ease. What a wonderful resource!