"Upload failed! (-1)" strikes again...

Just a few days after the last time this was fixed, the same problem with the "Upload failed! (-1)" message I was having before with uploading an updated version of my project to Realms has come back to strike again. I have tried closing both the game and the launcher and reopening them again, and I haven't even budged past 0% uploading progress without seeing this message getting in the way...