Can't manually import .qbo bank transactions file

The original answer was not incorrect, just not the best answer. There is no need to disable the account from online access. Here is the secret way to get these transactions into Quickbooks (on Windows or Mac).
Just be sure you are bringing the downloaded transactions into the correct account. I find this issue usually occurs with credit card downloads - as in credit card accounts that have more than one credit card (eg, one master and several sub accounts) associated with them.
Here we go. First download the QBO and save the file, say, on your desktop. Right click on the file and select Open With, then choose Notepad. (on a Mac use TextEdit). Now, look thru the info listed (starting from the top) and look for <ACCTID>. It will list an account number after this. You will notice that this account # differs from what is in QB. That is what is causing the problem. In QB, from your chart of accounts right click (control+click) on the account in question, select edit account. Copy down the account number listed here. Now, type it in Notepad, after <ACCTID>, replacing what was there. Voila!! Done!. Save the file. It should save as a QBO file. Double click on the file and the transaction will flow into QB seamlessly...  Matt (former online tech support for Intuit)

From the online settings tab.

Thank you!!

That solution worked! I am using the latest QB update (version 2017) and it is bizarre to have to deactivate the bank feed for the account in order to be able to import the QBO file. I tried everything, including deactivating and reactivating several times and nothing worked. There needs to be a patch to this offered to allow you to work around it so you don't lose hours of time scratching your head trying to reestablish a link to an existing account just because some linkage aspect has changed.

Thanks for the suggestion.

I have been having the same problem with QBO automatically pulling transactions from BoA since early March. I used to also be able to upload a QBO file downloaded from BoA; that has also ceased to work.

I happened to have an old QBO file from September, 2019 and compared it to the more recent ones. The only difference is that now, for each transaction, BoA is inserting additional fields, like this:

<MERCHCAT>

<EXPCAT>
 <CARDNUM>
 <CARDNAME>
 <MCC>

I removed those fields manually from the QBO file using Notepad, saved it, uploaded it, and VOILA ...joy

Now to figure out how to get BoA to stop including those fields at the source.

In the meantime I'm using the 'findstr' command from a command prompt window and it removes all the offending lines from a QBO file in one fell swoop; Then just upload the modified file, "stmt1.qbo" instead - yeeha :)

findstr /v /i /c:"<MERCHCAT>" /c:"<EXPCAT>" /c:"<CARDNUM>" /c:"<CARDNAME>" /c:"<MCC>" stmt.qbo >stmt1.qbo

Plug that line into a batch file, keep it in the same folder as the bad QBO file, and just double click the batch file to avoid the futile QBO and BoA support $hit $how 

I have 2 company files running on 2 different versions of QB, so that I can keep both companies open. When I attempt to download my transactions from Capital One it keeps trying to open the 2nd company, which does not have a Capital One credit card associated with it. To confuse matters, I also have 2 Cap One accounts in a single company. Can anyone help