On my IPad using multitasking is the only way to add photos, the upload button that shows up on my phone does not show up on my Ipad. I was trying to add a map to a conversation about VA routes, and the map would not be added, but all other photos worked. See most photos when dragged over from drag and drop show a plus and share it will be added…
Usually, what I do is go into Mobile view to upload photos. And I’m on iPad also. Just click the 3 bars in the top right to go into mobile view and the upload icon will appear.
The reason why the touch and drop of the map didn’t work is probably that it has another picture format. Normally, pictures are a .jpeg file. The map however is more likely a .png or a .tif file, and not a .jpeg format.
Try to upload like Chatta explained. That should work.