It's great to see a new face here in the Community. Two months is too long for an issue to be occurring within your account. Let's work together and try a few basic troubleshooting steps to help resolve the connection message, "8500 try again in a few hours."
Clearing your browser's cache will allow QuickBooks Online (QBO) to load as a fresh new page. This will eliminate any errors or glitches in your account. Here's how in Google Chrome:
Sign out of your QBO account.
Go to the three vertical dots in the top right-hand corner of the browser.
Press History and then History again.
Tap the Clearing browsing data option.
In the "Time Range" drop-down menu, pick All Time.
Once you're ready, click Clear data.
It's that easy. If you're using a different session, check out this link for the correct steps.
If this doesn't help, please provide me with the name of the credit card company you're trying to connect to QBO. Afterward, I'll be able to see if there are any on-going investigations with the credit card company for this error message.
I want to ensure that you get the support you need to get this banking error fixed as soon as possible. Let me know if this helps. I'm only a comment away if you need me. I'll be waiting for your response!