We have serious problem with our connected app. We have integrated our system with Salesforce and many of our customers use this integration to sync data in Salesforce and our system. For no reason authorization to this app became unavailable. And also we can't refresh access token via refresh. We didn't revoked any access to it or change settings. one week ago we had the same problem. but in a couple of days it was repaired without our intervention. (So I supposed Salesforce fixed it on their side? or idk)
But now it's fully NOT working. I tested and created new connected app. And they work.
Does anybody know the reason? What it could be? perhaps there is some limits of users to use connected app? Perhaps SF changed some policies.