You cannot change stick modes without first changing the above setting so I don't think the explanation was unrelated at all really, Sorry if it was BUT, The OP may run across the same problem with a different brand of Drone. Knowing why and how...
Most Drones actually have 3 flight modes ANGLE, HORIZON, ACRO (manual). In order to fly in horizon or acro the drone must be able to "pitch" beyond its "Moron" setting. Checking the "M attitude" is what changes those numbers for DJI Drones and...
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Fair point, but about five years too late - that horse is a dot on the horizon, so locking the stable door and having the groom police the yard is a redundant action.
Decisions have already been made - being watchful and informing on...
This was exactly it. I don't know why the attitude limit was locking it out, but unchecking the option allowed selecting the different modes. Thank you so much!