Installation of HACS on HA green

Last week I purchased a “home assistant” green and I’ve had no success in setting up HACS.

I then watched the instructive video https://www.youtube.com/watch?app=desktop&v=a4lSlN6EI04.

Following the instructions, it went well up to the completion of the authorisation. However, the “Success!” Pop-up message didn’t happen and there was no HACS item in the left-hand sidebar.

Using “Studio Code Server” the following message popped up:

Any help offered I will greatly appreciate.