I just went through the workflow myself. Although the tool prompted me with the same warning the upload went through successfully. Just to double check if click on file is 'Sign Out' and your user name listed?
Have you been able to upload or publish a service/service definition to ArcGIS Online successfully before? What is your user type and role in your ArcGIS Online organisation?
Yes, I see the 'sign out' with my name next to it
I am a publisher
Also, I can load the sd file through the web portal and publish it. But when I try to visualize or add the new hosted feature layer to a map, then there is a general error.
Best Wishes, Michael
I appreciate the screenshot and the additional information. If the hosted feature layer created from the service definition also fails to load, my suspicion is an problem with the service definition. I recommend recreating the service definition with test data. If you have ArcMap installed you should have access to the following file geodatabase.
Example File Path: C:\Program Files (x86)\ArcGIS\Desktop10.6\TemplateData\TemplateData.gdb
What method did you use to create the service definition initially?
I used the example file, but with same error.
Before publishing I get a notice about certificate expiration for the portal server (see attached)
This is strange, because when I go through the web site, the certificate is fine.
regarding you question, originally, when I got the error, I tried to do it again in two stages by saving as definition file and then uploading.
I was told, the server is supposed to be updated soon, so I'll postpone this matter until after the update.
Thanks for the update, it looks like ArcMap doesn't trust the certificate of the ArcGIS Server or Portal you are trying to connect to. Is there any difference in the URL you are using to connect to Portal or ArcGIS Server in ArcMap and the URL you use to access Portal in a browser?