I use Google Slides for teaching art history, and my files often contain lots of images. Today, I was working on one of my presentations, and all of a sudden, most of the images disappeared / they failed to upload. They now appear as grey boxes with an exclamation point in the center. I'm worried I will have to re-do the entire presentation. This will take a lot of time, because not only do I need to re-upload the 200+ images, but I also need to find the images which are saved in various places on my computer/hard drive, figure out the order of the images, etc.
Is there any way to recover the files once they appear as the grey box with the exclamation point? Do I need to re-upload all of my images one by one? Please help! Thank you!