Upload Failed (-1) Java Edition

Every time I try to upload a world from singleplayer saves into my Realm it gives me the error message "Upload Failed! (-1)" before the bar even starts to load. I have been trying to upload worlds since yesterday but it never has worked. I also had the same issue a few months back in 1.13.2 but my subscription was about to end anyway so I just forgot about it. My world does not have any datapacks either it's just a save file I made and played for around 10 minutes.