I was using the Approvals feature for the first time in an environment yesterday and when I tested my Flow. The approval seemed to get stuck in running state. This was a solution dependant Flow.
By chance, I looked at my list of solutions and there were two new solutions in my CDS environment. So I guessed that the reason the Approval step was still running was that it was importing these two solutions.
When I checked back later in the evening the Flow had failed with the following message -
"The request failed. Error code: 'CdsInstanceProvisioningIncomplete'. Error Message: 'A Common Data Service database for this environment has not completed provisioning or does not yet support the requested approvals functionality. Please try again later.'."
Which sort of confirms my assumptions.
I don't see this as a bug so thought I'd raise an idea to build in a message that warns the user when a solution is being imported and to wait so as the user doesn't waste time trying to diagnose the issue.