Hi John,
You will likely need to reduce the file size below 1mb. I believe there was mention in a past thread that image file size upper limit is 1mb. Looking through a few posts I see that many image sizes are well below 100 kb. You most likely already checked this thread but in case you have it covers resizing etc. etc.
https://clockrepairtips.com/forum/viewtopic.php?f=2&t=1450
I hope this helps John,
Best, Dean