Nexus error uploading artefacts 502

When attempting to upload to a specific Repo we get 502.
The Repo has a proxy configured, both the Repo url and Proxy url return what is shown “XML File does not appear to have any style information”, but you can still browse it using the browse option. Confirmed with admin that both Repo and Proxy are configured correctly. Suddenly stopped working a few days ago.

Any input appreciated. If it is the proxy at fault a way to prove this would be useful too.

Found to be due to an expired API key. Would have hoped for a better error for this however it’s now working again. Still get the xml errors but assume that’s just due to accessing via a browser.