I have the same exact problem with the Capital One credit card bank feed. I cannot deactivate the account in Quickbooks. I had to do the Solution 3, which is the manual deactivation of Bank Feed via Excel posted by Paying Customer. Make sure to follow the exact instruction by Paying Customer in his thread.

https://quickbooks.intuit.com/learn-support/en-us/banking/re-unable-to-disconnect-bank-feed-from-dis...

When you start a new activation, make sure to use the "Capital One - Credit Cards" one and link it to your current Capital One card account in QB Desktop.

I think the issue is caused by security change either with Capital One or QB, and it requires you to reconnect. The big problem is when you cannot deactivate the account in QB, which then you spend a couple of hours trying to figure out the solution. Once you can deactivate the bank feed for your account in QB, you can reconnect and relink OK.