Unable to Airdrop edited .NEF files from Photos

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

HEIC are not raw photos. It is a very efficient compressed format that Apple has adopted to create much smaller files to we can have more on an iPhone or Mac. However, it's not used widely so to use in many other apps or on the internet they must be converted to a more compatible JPEG format which can be done by exporting out of the Photos library as an edited photo.

There's no such thing as an edited NEF, or any raw file. IN fact, a Raw isn't really even a file, just a sensor dump from the camera.

When you edit a NEF in Photos or similar apps (i.e. parametric editors), your decisions are stored in the database, and applied live to the NEF each time you view it. But to share the file in edited form you need to save it as an image file - I,e Jpeg. tiff or whatever.

Edited photos? I thought we were talking about raw files specifically.