[Error when uploading covers to HC]

I optimized by database but did not fix.  Currently rebuilding lists, but that is taking a while.

 

[Error when uploading covers to HC]

600x600 dpi in JPG

[Error when uploading covers to HC]

"Ran into some trouble trying to display that picture.  Object reference not set to an instance of an object"  

Only option is to click on OK and return to CB.  I am never able to view the cover.  I recently increased the quality of my scans as I thought it would not be a problem now that CB is advertising 4K.

[Error when uploading covers to HC]

Hello.

I am using v21.0.2.1790 and started getting this error on some cover files I added.  Is there a limit to the size or quality I can add?