@laurie oh bummer! I’m looking forward to seeing your sweet little Spike.
A couple ideas when for when you download your pics and have failed attempts.
You have it figured out enough to post. So when you try again, wait until you see the green check mark ✅ on top of your photo once it’s downloaded, showing that it indeed has secured it into the message. Initially it will have a line or bar running through the pic as it downloads. It gradually fills in to all dark grey, then the bar disappears and is replaced briefly with the check mark. After that you can go ahead and post the photo.

Also as you are looking to post a picture, if you end up scrolling and lose the message to add or drag photo here, or if the screen for you photos disappears, you’ll just have to click on Add Photo/Files again as it’s very touchy. Doesn’t like it when you inadvertently move out of that little window.
See if that helps! Lori