Prometheus Datasource Metric Browser Wait indicator spins forever

I’ve successfully setup Prometheus (V2.2.1) as a datasource in Grafana (V8.3.3).
When I setup the datasource to point to the server at http://<ip_address>:9090 with server access and the HTTP Post method.

When I click on the “Metrics browser” on a new panel, the “Loading labels…” message and spinning wheel stay forever.

I verified in the Prometheus UI that there are about 300 metrics.

Also having this issue after upgrading Grafana from 6.2 to 8.3, any help would be great cheers