You may encounter this error when performing any of these actions on a flow that uses premium connectors:
Importing the flow
Enabling/disabling the flow
Saving/Save as on the flow
Any other permanent modification to the flow
This error means a Power Automate license is required for the current user to perform the action (a Power Apps, Dynamics 365 or Office 365 license is not sufficient).
Users who are shared a flow with premium connectors (not belonging to a "Per Flow" plan) will each need a "Per User" plan to edit or manually trigger the flow.
If saving/modifying the flow was possible for the same user previously, it is possible that their license has expired.
Purchase a "Per User" plan or "Per Flow" plan for Power Automate
Alternatively you can start a trial for the "Per User" plan lasting 90 days after which you will require a paid plan to run/edit flows using premium connectors.
All these options (with additional information) are available here: flow.microsoft.com/pricing