Some of the map service layers from the National Oceanic and Atmospheric Administration (NOAA) website are not visible after exporting to a PDF file from ArcGIS Pro.
When a cached map service is enabled with dynamic-layer capabilities, ArcGIS Pro and the print service makes '/export' calls instead of pulling cached tiles during an export to a PDF or PNG call to generate the image at a higher resolution. The map services used in this bug do not have any contents themselves. As a result, '/export' calls return blank images. Therefore, the output from the ArcGIS Pro Export operation produces an empty output. Once the service provider updates these map services, it starts working in ArcGIS Pro.