GIMP Version: 2.10.18
Operating System: Windows
OS Version: Windows 10 Home OS version 10.0.18363
GIMP Experience: Basic Level

List any relevant plug-ins or scripts:
fresh install. I have no known plugins/scripts.

List any ERROR messages you received:
(-) GIMP Message
Saving 'C:\Users\...\Pictures\IMG_2172.JPG' failed:
Permission denied

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I recently uninstalled Gimp when I discovered there was an update and installed the new updated program. I opened a .JPG and exported to the same file name with jpg file extension and received 'permission denied' error. I've been able to make changes and export to the same filename before, so I'm not sure why it won't let me overwrite the file with the edits. It does allow me to export to a different extension such as PNG.

Thanks,
Last checked for updates 4/25/2020

Did you check the "permissions" your have for the file you are talking about?
Maybe it has only "read" permission.

Are you able to delete the file you want to over-write?

If you can't then is what dinasset said.

Problem solved! Thank you! That was it. My file was read only. I didn't expect that, since they were my photos, except I had downloaded them from an email. Thanks for your help!

I've had the same error.

By going through the following order of steps, the error no longer appeared:

Import or drag your image to GIMP
Crop/ Crop to content
Scale image
Save
Export