Error 590 with Mercury BankIt was working just fine until a couple of weeks ago. Now I can't re-connect the accounts.

You have to connect your bank account to bypass the error you're encountering, info2175. I'll provide more details on this below.

In QuickBooks Online, encountering Bank error 590 indicates that there is a problem coming from your bank's end. As a result, you're unable to sync transactions between your bank account and QuickBooks Online.

To resolve this issue, since you've mentioned that your account was disconnected a few weeks ago, reconnecting will reestablish communication between your bank and QuickBooks. You can also perform manually uploading transactions within your account, ensuring your financial data is up-to-date. Additionally, getting in touch with your bank to check if they've resolved the issue on their side can also be beneficial.

Moreover, you can check to this page for further information on how to fix bank errors in QBO: Fix bank errors 355, 580, or 590 in QuickBooks.

Lastly, I'll share this article in case you want to categorise transactions uploaded to QBO: Categorise online bank transactions in QBO.

I trust this information will help you get back on track, info2175. Please know that you can revisit this thread if you need further assistance regarding bank connectivity. We're always here to help.

Try opening your QBO account on any private/incognito browser.

I've tried it all. What happens if I disconnect the accounts and reconnect them again?

I appreciate your compliance with the steps my colleague outlined, Info2157.

Disconnecting your bank account from QuickBooks Online (QBO) will pause the downloading of transactions, and reconnecting it will start the process again. Let's tackle this topic further.

In QBO, uncategorized transactions won't appear in the For Review tab if you disconnect your bank account. Also, note that you can't download transactions over 90 days old once you reconnect it. However, you can upload these old transactions manually.

You can gather additional information by scanning this article: Disconnect accounts connected to online banking in QuickBooks Online.

Once your transactions are ready, you can start categorizing them to keep financial records neat and organized, simplify tax filing, and assist in strategic business planning.

Tag my name in the comment below if you have follow-up questions about QBO bank connections or need help performing other workflows. I'll be at your service once I receive notification from you.