I’m having the exact same problem. The backstory is, I’ve been using my myntkat wordpress account with myntkat.com for years, I just started another blog and thought I could just use a different gravatar on the same account. After connecting the new shinylife.co.uk with my myntkat account I realised that jetpack didn’t work that way, so I disconnected it, removed it from my wordpress account and started shinylifeforme as a new wordpress account to use.
Now when I try to connect shinylife.co.uk jetpack to shinylifeforme account, it says it’s connecting, it even brings me to the shinylifeforme wordpress account. But when I check in the jetpack settings on shinylife.co.uk it still shows myntkat. I’ve disconnected, reinstalled, nothing works, it keeps saying it’s connecting to the new account but still shows the old account every time.