I am using the data from that link so that is a bit odd.
One thing that is different is you are using the file name as the web layer name. Does it contain a period still prior to jpg? It is hard to tell if you added an underscore. If it is there, then that should not allow it to publish, but Pro should throw an error that can be dismissed. If the period (.) is there, can you remove it and see what happens?
If it is removed, have you tried removing the layer and re-adding it? Or trying a new map?