How do I get "pay here" on the invoice? I added Paypal and Stripe, but there is no "pay here" when I send an invoice...

Afaik, you are unable to create a payment link to accept PayPal or Stripe and put it on your invoices of QB Online. You may create invoice on PayPal or Stripe, then utilize the 3rd party app as I mentioned in the earlier post. 

As another option, if you are trading merchandises, create your own webstore and accept PayPal and Stripe. You don't need to create invoice individually to your customers.

https://get.sellfy.com/mystore