It's good you're looking to link your merchant account to QuickBooks. I'll be happy to look into this and provide more info.
Currently, QuickBooks has its own Merchant Services system. Here's a link with more info on our Merchant Service's Payments system: Online Payments. If you're using this system, feel free to send me a screenshot of what you're seeing when you try to link it. Are you getting error messages? How long have you had the merchant account for? Don't hesitate to share as much info as you can while keeping in mind that this is a public Community.
I'm using a Canadian credit card processing solution and want to be able to connect to it but quickbook does not give any option under payment (see attached screenshot). The only button available is "learn more"
I want to ensure you'll be able to connect your merchant account successfully to QuickBooks Online (QBO).
You can simply click on the Learn more button and follow the on-screen pop-ups or instructions to link/set up and activate your payments account to QBO.
On the other hand, I'll also suggest getting in touch with our Support Team for further assistance. This way, they'll be able to check why you don't have the Connect button and check if your merchant is still active.