A connectivity issue could be caused by maintenance on the bank's server, a setting in your account that needs to be adjusted, or errors, which often include a code. Did you receive an error code?
I'll help you check to see why you can't link your Royal bank account, and I'll also provide an alternative to bring your transactions onto the Banking page.
Let’s start by signing in to your bank account to see if there is an announcement about maintenance or anything related to online banking. You'll also want to check if there's a switch in your settings that needs to be turned on. If none, download your transactions in a supported file format so you can upload them to QuickBooks. This is the other method that I mentioned above. Here is an article for your reference: Manually upload transactions to QuickBooks Online.