It looks like this was a Prometheus\PSU config issue on my end. I downloaded the latest version and had to use the following command line to start the OTLP connector.
.\prometheus.exe --web.enable-otlp-receiver
I also had to update the URL used by PSU.
"OpenTelemetry__Otlp__Endpoint": "http://localhost:9090/metrics"
Once that was done, I am now receiving metrics in Prometheus from PSU.
