I cannot connect Payoner account to Quickbook. I see the error 350

Hi there, max-chut-neurons.

Thank you for visiting the QuickBooks Community. I'll be sharing details about being unable to connect the Payoneer account to QuickBooks Online and the error 350. Then, let me point you to the right support team to assist you further on this syncing between the Payoneer account and QBO.

The mentioned concern above has been recently tagged as an ongoing issue. Our product engineers are now working to fix this as soon as possible.

For now, you'll have to get your transactions from your bank or credit cards and manually import them into QuickBooks Online ad workaround. You can open this article to see the steps on how to perform the process: Manually upload transactions into QuickBooks Online.

Then, I suggest contacting our QuickBooks Support Team so they can add you to our notification list. This will help our engineers determine the number of affected users. You'll also receive an update through email once this has been resolved. 

Here's how:

1. Sign in to your QuickBooks Online company.
2. Click the Help (?) icon.
3. In QB Assistant, enter the topic you need help with. You can also enter questions.
4. Choose Contact Us to connect with a live support agent.
5. Choose a way to connect with us. Then, enter the needed information.

Lastly, you may refer to this article to see steps on how you can review your entries by matching or adding them to avoid duplicate transactions: Categorise and match online bank transactions in QuickBooks Online.

Let me know if you have other banking concerns or questions about managing transactions in QBO. I'm always ready to help. Take care, and I wish you continued success, max-chut-neurons.