When opening an existing project where, for whatever reason, the credentials or authentication is not available/broken/cancelled it is not currently possible to tell Pro to 'just ignore it and move on'.
It will keep trying to load the layer and ask you to authenticate.
Add a feature to "Skip similar requests" to the sign-in popup so that we can load the project and remove the offending layer.

It seems to launch the popup ~15 times before it realises you had a reason for cancelling it the first 5 times.
There is no indication in the sign-in message what the sign-in is related to.
Bonus points for showing the source of the login request in the popup.
There are tricks to fix this if you know a layer has an issue beforehand, but it would be nice to have a sanity check in place if a project is opened without my 6th sense working on a Monday morning.