Here is the support page with the steps.  You have to deactivate the bank feed & reactivate:

http://support.quickbooks.intuit.com/support/Articles/HOW16085

Resolution for 'America accounts issue: 'I have not changed any settings on my Bank of America accounts. I had no problems downloading up until 3 days ago. Now I get an error message OL393. What can I do?' available: Yes.

The America accounts issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the America accounts issue yourself by looking for a resolution described in the article. If it is a complex America accounts issue or you are unable to solve the issue, you may contact us by clicking here or by using other America accounts support options.

For more information about resolving issues related to America accounts in Quickbooks/QBO or to get support for the issue 'I have not changed any settings on my Bank of America accounts. I had no problems downloading up until 3 days ago. Now I get an error message OL393. What can I do?', click the link below: