I am trying to add a symbology class to a layer but the options are greyed out. I believe it has something to do with the warning that says "primary symbology relies on one or more fields that are invalid." However, I already have working, classified symbology. When I add a field to the blank Field 1 drop down box, the error goes away but my pre-existing symbology is destroyed.
Duplicate your layer (copy/paste) in the content pane then import the symbology from the original layer to the copy. As the import process let you choose the field to use for symbology you will be able to reset the field and hopefully have a layer without error (you may have to do the import two time for it to work, don't know why…).
If this work you can remove the original layer with the error and work on the copy that should not have any error.
