If receiving error message in QuickBooks "cannot read properties of null (reading 'getMonth') when trying to access bank register, then how does a user reconcile error?

Thank you for reaching us in the Community, @ephgoa. I'm here to help get this resolved. 

If QuickBooks Online (QBO) encounters "cannot read properties of null error," it is most of the time associated with cache-related errors. QBO uses cache to store frequently accessed data or instructions which can become outdated or corrupted over time. To fix this, I recommend performing browser troubleshooting steps. 

For Google Chrome / Microsoft Edge / Opera:

• Windows: Ctrl + Shift + N
• Mac: Command ⌘ + Shift + N

For Firefox:

• Windows: Ctrl + Shift + P
• Mac: Command ⌘ + Shift + P

For Safari:

• Shift + Command ⌘ + N

If you are successful in accessing the register through incognito mode, please proceed to clear your browser's cache. This will remove and fix any problems and optimize the program's performance. Additionally, you can use other devices and supported browsers to verify that everything functions as expected.

For future reference, I am adding an article that provides guidance on resolving any reconciliation issues if you happen to encounter one: Fix issues for accounts you've reconciled in the past in QuickBooks Online.

You're always welcome in the Community should you have further updates on the error you've encountered when accessing your bank register in QBO. We're here to assist. Take care.