Same thing happened again to me last week, when I had to reauthorise my Barclays bank and Barclaycard business accounts.  It would go through and reconnect and say it was successful, but when back at the Banking screen say it wasn't and needed to be reauthorised.  Tried the usual trick of other browsers, incognito windows etc but no luck.  In the end, I had to delete the connection (after first matching all outstanding items) and then make the bank connections again, asking it to only pull transactions from whenever the last date it connected.  That worked.

No doubt the same thing will happen when it needs re authorisation in 60 days.  It's clearly broken, but QB haven't bothered to fix it.