I have a Next.JS app with DocuSign integration using Authorisation Code Grant oAuth. It was working fine, but the app is un-reviewed. As I tinkered with it, I flipped the switch that said that my app can store a client secret so I could try JWT auth instead of authorisation code grant. This broke everything, but when I try to switch it back, I get “This integration key could not be updated. Please try again in a moment.”. It’s been days now. I can make a new app, but I get the same thing when I try to edit it.

I have checked the callback uri and cors addresses for non-allowed characters, as per the other stack overflow question on the subject. They’re fine. No issues there.
I expected to be able to save the settings changes and get on with getting the app working correctly.