I too am having this issue. I went to reupload my main world my friends and I play through realms because I was updating a datapack. I am many attempts in, but consistently have the realm upload fail at the verifying stage, giving the 504 error. That is, if it even reaches that stage. I've also had multiple instances of the upload failing at any percent between 0 and 100 saying “Upload failed! (-1)”. In the past I've had minor issues with realm uploads, but ultimately was able to eventually upload a world successfully after a few attempts. This, however, is ridiculous, considering I still haven't had a successful upload over the past 4 hours of attempting. This desperately needs to be fixed!
Grayeet
I too am having this issue. I went to reupload my main world my friends and I play through realms because I was updating a datapack. I am many attempts in, but consistently have the realm upload fail at the verifying stage, giving the 504 error. That is, if it even reaches that stage. I've also had multiple instances of the upload failing at any percent between 0 and 100 saying “Upload failed! (-1)”. In the past I've had minor issues with realm uploads, but ultimately was able to eventually upload a world successfully after a few attempts. This, however, is ridiculous, considering I still haven't had a successful upload over the past 4 hours of attempting. This desperately needs to be fixed!