This error can occur if QuickBooks is unable to verify your bank's website. There are two ways to ways to get rid of this error. You can either reconnect or update the connected account manually, or connect a new one.
Let's try the first solution which is reconnecting or updating your account manually. Let me show you how:
You can also follow Solution 2 in this article if you need more troubleshooting steps to resolve the error: Fix Banking Error 324 in QuickBooks Online.
I'll be around if you need anything else.