Unfortunately, I've suddenly found that I cannot publish web layers from ArcGIS Pro to ArcGIS Online. The job gets stuck on Uploading Service Definition for a long time and then will fail. I've also tried generating a service definition file and uploading that directly, and it also fails. I've created a support ticket, but in the meantime, is anyone familiar with how to resolve this issue? I'm using ArcGIS Pro 3.2.1 and was able to upload web layers without trouble just 2 days ago.