I did everything as per the instructions, but it failed.
After much experimenting, I discovered that I needed to CLOSE the browser and reopen it before the changes took effect. After that, everything worked fine. Before that, the Steem keychain kept loading instead of the Hive keychain.
I made a tutorial of what I discovered, not knowing that you had made one. (I just found yours now.) You may wish to add the browser re-boot requirement to your own tutorial since it gets more views than mine.
You can only have one keychain running, if you are still trying to use Steem, I recommend using two browsers, one for Steem and one for Hive.
Hmmm... Interesting, since I have both keychains showing on my browser and 2 tabs open. One for Steem and one for Hive. Both seem to function as expected after I closed and re-opened the browser following installation. Any ideas about things that could go wrong?