Which theme you are uploading in shopify store?
have you purchased from theme store?
Hank here from Shopify.
Are you trying to upload a theme? Or is it in relation to an app that you are receiving the message?
If it is relating to a theme, where did you purchase the theme? Also is the same issue happening for you when using incognito mode?
If you can tell me a bit more information, I can take a closer look at this for you.
All the best, Hank