Go to the control panel, all elements and credentials. Or, search for "Credentials" ("Legitim") by the windows button.
Choose "Windows-credentials" ("Windows-legitimationsoplysninger")
Choose the olap.keepers.nu access and press either "remove" or "edit"
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Delete existing connections in Microsoft Excel
Go to "My data sources". Choose the connection you need to delete, and press delete.
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Check that the connections are gone in Excel (Data, Existing Connections)
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Restart the computer.