I had the exact same issue. I created a business paypal account with the same email that I used to set up the Shopify store. From there you go to paypal, click profile settings, click update on the email portion, click send confirmation email for that specific email address. Go to your email and confirm the email address for paypal. Then, go to shopify, make sure that email for that paypal is the email you used for the express checkout. If it is not, disable it, re-enable it, and make sure you use the paypal you just set up. I had this exact issue for a while and it turns out I was using a private paypal that wasn't the same email I used for the shopify store; once I fixed those problems I did not confirm the email. After I did all of those things the pending payments were immediately processed.
Guys! Not sure if this can help but try to unlink your Google account at <General> on Shopify. I was first so confused like some of you did as well cuz I literally followed the steps thousand times and not working at all. However, when I disconnected the Google account, the payment immediately went through. So I'm thinking this might be one of the factors causing the pending cuz of using a third-party logging into your Shopify account.
Really hope this can help!!!!!