We're experiencing the same issue. A "unexpected error please contact" message from both the API and from the Appstore dashboard.
The last successful report we received was on 18th July.
Ado_
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Same issue since 23:00 BST
We were having the same issues since Yesterday.
But seems that is working again. I've managed to download the salesReports via the API: https://api.appstoreconnect.apple.com/v1/salesReports