self-paced learning - can't mark an event as complete, says "forbidden"

Summary:

I am in Dev playing around with Self-paced learning. I created an event yesterday and assigned the learning. Today I am trying to mark it as complete for each of the learners. I can go to Learning assignments and mark it as "bypass complete" on their individual learning profiles, but when I go into the event and try and mark it as complete from there, it lets me fill in the completion details, but then when I hit save, it gives me an error saying forbidden. Is there something we are missing with our configuration?

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