Unable to update supervisor on Home Assistant Blue

Yesterday, I set up a brand new Home Assistant Blue. I was able to update the OS to Home Assistant OS 6.2, but when trying to update the supervisor from 2021.03.6 to 2021.06.8, I’m getting an error message and this in the log:

Logger: homeassistant.components.hassio
Source: components/hassio/websocket_api.py:109
Integration: Home Assistant Supervisor (documentation, issues)
First occurred: 12:03:13 PM (1 occurrences)
Last logged: 12:03:13 PM

Failed to to call /supervisor/update - No supervisor update available - 2021.06.8

What can I do to fix this?

Make sure the HA Blue has internet connectivity. Try reboot Home Assistant —> Try Upgrade Supervisor —> Fail —> Reboot Supervisor —> Try again to update Supervisor —> Reboot Home Assistant Host —> Try once again to update your supervisor.

The system is connected to the Internet. The outlined sequence doesn’t seem to help.

The system seems rather confused about its state. Now it thinks it’s running OS 5.13 again, but when trying to update to 6.2, it says it’s already installed. Please see this screen recording:

Just maybe, can you try clearing your browser cache? If possible, you can try to use other browser to access HA page.

That was it. Thank you! Didn’t even think of the possibility that it was a pure front-end issue.

Browser cache invalidation (or the lack of it) seems to be a common issue with HA.