I cannot post photos from my iPhone photo library. I get a “invalid file type” message.
This has happened in the past.
Hopefully the glitch can be fixed! Thanks.
iPhones use a unique Apple format for photos, HEIC. You can get several free programs (or commercial ones) to convert HEIC to JPEG or something more standard. You can also set the phone to use non-HEIC images going forward, but I don't remember how.
If it is happening to photos that you have taken with your camera then they are probably being saved in HEIC format. Go to Settings -> Camera -> Formats and confirm that Most Compatible is selected. That will save future photos as .JPG.
I’m not sure how to convert HEIC to JPG for existing photos.