Can you clarify if you're using the desktop app or the Website when trying to upload?
It sounds like you're using the Website (since you mentioned the upload button), so it'd be a great idea for you to try a different browser or an incognito tab, to see if you still have issues uploading.
Can you try this, and let me know if the results are the same?
I won't be able to try to move phot files until Wednesday morning, but I'll let you know. I used the DB app on the Mac--I tried so many things, I honestly cannot tell you if I was ever just on the DB website...I don't think so. I think I tried only from the DB icon on the Mac.
The Mac belongs to a friend who I help with all her correspondence. She has had trouble for years with the same problem of moving photos to DB and has taken heat from the organization for whom she photographs. I thought it'd be so easy since I am a PC user and long-time paid user of DB. Not so.
I will try logging onto her DB account and see what happens. At least it's a different angle. But would trying putting the album on the desktop, opening the album, copying all photos in that album, and then trying to move to DB work? I'll try anything.