Hey Mitchell,
For this kind of issue it would be best to try and narrow down the problem, this is what I would do first:
1. Open the original map document, and then open another, blank map document next to it.
2. Highlight everything in the table of contents in the original map document, then drag/drop it in the table of contents in the new MXD. This copies the content from your original map document into the new map document, along with all the symbology.
3. Try to publish from this new MXD to see if that resolves the issue
If the same issue persists after trying a new map document, try adding/publishing one layer at a time from the new map document to see if one or many of the layers fail to publish successfully. This will involve dragging one layer from the original map document and dropping it into the new map document > then publish the single layer from the new map document to ArcGIS Online.
If it's successful, remove the layer from the new map document and move on to the next layer from the old map document. Do this for each layer in your old map document until you find one that doesn't work, or until all the layers are published successfully and work correctly in ArcGIS Online.
The above steps will help narrow down if the issue is with the map document, a layer (or multiple layers), or both.
-Jacob
