If you no longer wish for OneUp to connect to your bank to sync transactions, you should turn off sync in the bank settings.
First, Go to Accounting > Bank Activity and click the bank you want to turn off sync for:
In the Bank Activity view, click the settings gear and Edit Bank Account:
Editing the bank account settings, scroll down and click to open the Advanced section.
Next to Bank Synchronization click Off.
Click Done to save.
You will now see an Import Bank Statement button instead of Sync with Bank button.