We are actively investigating this and working on a solution for these Token Exchange failures.
Current Mitigation: After the Flow action executes a connection and encounters a Token Exchange failure, the connection is flagged as broken. At this juncture, there are several options available to rectify the connection issue:
1) User opens an incognito browser window to relaunch the application. Upon app relaunch, Power Apps will re-authenticate the connection if it detects that it is broken (without any user interaction if possible).
2) The user navigates to the connections section on make.powerautomate.com or make.powerapps.com to manually re-sign into the connection.
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I've opened another ticket last week because I don't think this is a fix to the issue. I'm asking that the product team reevaluate their recommendations.
I would recommend opening a ticket with Microsoft so more traction can be had around this issue. In our case, it seems like the PowerApp doesn't recognize that the associated Power Automate connections may need to be refreshed, so the user can launch the app without issue, but the user isn't notified that they have broken connections from within the associated Power Automate.