Error Unknown error

I receive error notifications every time I try to submit my videos. I used to be able to correct this problem by either trying different browsers or clearing browsing data like cookies, but neither are working lately.
Does anyone have a solution to this problem? I see many others with same problem, but also see others upload 2-3 videos a day.
I have tried Google Chrome, Mozilla Firefox, and Opera on Windows PC.
Thank you in advance for any help.