I was having similar problems today, new images throwing an unspecified HTTP error when uploading, not showing thumbnails in the Media Library, just grey placeholders (although previously existing thumbnails were fine), no image edit options in grid view.
I was just advised on another forum to use the Force Regenerate Thumbnails plugin. I tried it on one test image, freshly uploaded and displaying all these problems, and not only did it get the thumbnail back, it’s fixed the upload and edit problems too, I’m now uploading without errors and able to edit as before. I hope this helps.