I'm getting error 355 which is telling me QB is having trouble getting my bank data. How do I fix this?

Thank you for posting here in the Community, @user31194. 

Error 355 is a temporary error impacting your bank connection which should normally resolve within 48 hours.

To refresh the connection between your Bank and QuickBooks, let's run a manual update:

1. Go to the Banking menu.
2. Select the bank you need to update. Blue indicates the selected bank, grey means it's unselected.
3. Click the Update  button.
4. Enter your Multi-Factor Authentication (MFA) credentials (if prompted) and then click Continue Update.
5. When the update is complete, you'll receive a notification and if successful, you will see that the date of last update and total number of transactions have changed. 

For your reference, please check this article: Fix Online Banking Errors in QuickBooks Online (QBO).

However, if the error persists for longer than 48 hours, I suggest contacting our QBO care team. They have specific tools to do a remote session and verify what causes the issue and fix it for you. 

Also, learn more about the What's new in QuickBooks Online-May 2020: Introducing this month’s list of updates such as Dashboard Cash Flow widget, New online Bill Pay, and more. Please visit our QuickBooks Blog for details. 

I'm only a post away if I can be of additional assistance about online banking errors. Stay safe and take care always, user31194.