Do you mean your bank account was disconnected from the Banking page?
An account will be disconnected when you edit your account info and put a check in the Disconnect this account on save checkbox. This process is done manually, so if yours was lost without your input, please contact our QBO Support so they can check it using more tools. Check about disconnecting accounts connected to online banking for your additional reference.
On the other hand, you can reconnect your account, but this will redownload your transactions in the last 90 days. Therefore, you'll want to exclude those you've already added to your bank register to prevent duplicates.
In the For Review tab, select the checkbox of the transactions to be excluded.
Click Exclude.
Please let me know if you have more questions in mind. I'm here to help.
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