Thanks for sharing the complete details of your account, TeriF3339.
I'm here to get you pointed in the right direction for signing up to QuickBooks Payments.
From the information you've provided, it looks like the email address was connected to two company files. This might be the reason why it won't let you sign up since merchant accounts can only be linked to one QuickBooks company.
I'd love to make sure you're able to do this, however, I won't be able to do that without asking your account information. Since the Community is a public forum, I don't want your details displayed here for security purposes.
I recommend contacting our Merchant Services Team. They can check your account and ensure that it is set up correctly. You can find their contact information through this link: QuickBooks Merchant Services.
As for the other question, as long as you've set up your email to send invoices, you can add the Square payment link anywhere in the email text.
Once done, manually record the payment in QuickBooks.
That should get you back on track. It's my priority that this is resolved for you, so please let me know how it goes. I'll be keeping an eye out for your response. Have a good one.
