- Temporarily turn off content blocker tools like adblockers, VPNs, browser extensions, and firewalls.
These can interfere with the upload process. If possible, configure these tools to allow Riverside.fm. (More info.)
- Close any other Riverside tabs that you still have open, then open only the Upload page.
If the steps above do not help, follow the instructions in this article to open specific firewall ports that allow your computer to connect to Riverside.