Unable to export photos onto external hard drive

Hi! I'm having some trouble with exporting my photos. I have been using Lightroom Classic and photoshop for years, I've been using my external hard drive to store all my files for the past year. I've never had any trouble exporting my photos directly onto the external. I recently switched from Windows to MacOS, I edited on both photoshop and lightroom today, I finished my edits and went to export but on both programs it just says that it is un-writeable. I am able to export onto my computers hard drive but not the external. I also am not able to move my photos from downloads to the external. I use only the external hard drive for photo storage, how can I save my photos to the external?? 

I tried adding both programs to accessibility and such, it forced me to delete all my edits on photoshop so that it could restart, but it still is not saving after restarting the program. 

how do I fix this???