I recently encountered this same issue and what’s odd is that the picture dimensions have been unchanged over the past 12+ months that I’ve used the photo albums. The picture sizes have all been 1-2 MB each while the dimensions have been 3840 x 5760. Standard exports from Lightroom. This has worked flawlessly up until two weeks ago and I’m at least 50 photo albums in.
I tried the above admin changes and that didn’t resolve it. What did work however was unchecking Photo Albums -> Settings admin page Table VII-D4. Not sure how I feel about disabling the check but I can now upload again. Any thoughts or other suggestions would be great, thanks!
cheers,
Shawn