User unable to launch apps - has hundreds of active connections (!?)

One of our PowerApps users has recently started seeing launch errors in all of his apps, with a combination of the following two error messages;

Connection not defined for this Service.

The app didn't start correctly. Check that you are online, and try refreshing your browser.

However, when we look at his connections (via make.powerapps.com > Connections) he has literally hundreds of connections showing as active. It seems to be impossible to select multiple connections for deletion and to remove them one at a time would be onerous in the extreme.

I have tried un-sharing the app and sharing it again, re-publishing the app, and changed his membership of the Sharepoint group providing access to our lists, all to no avail.

Does anyone know what could be driving this error?

Categories:

Connectors

Connecting to Data