Not able to enable editing of specific field

[MollyMoore]

I have a web map with forms enabled so that our field staff can collect data out in the field. The source of the layers in the web map is a feature service built from an SDE database. There is one field in particular (and consequently the most important field) that is not able to be edited in Field Maps and I am unable to check the box to allow editing in the Forms menu or in Field Maps configuration - it is grayed out. I double-checked the SDE database and the feature service layers and this particular field is not set to read-only and is set to allow editing. All the other fields in the layers seem to be behaving as expected. Does anyone have any other suggestions for checks about why a particular field is not able to allow editing?

[MollyMoore]

Some additional info after doing some troubleshooting: if I construct the map in Web Map Classic, this does not seem to be an issue (this also takes care of the annoying alphabetical field arrangement issue). Using the Collector app also seems to allow this specific field to be edited. I'll try to reconstruct all the maps in web map classic, but this is incredibly frustrating.