Hyde here from Shopify.
If you're using a third-party payment gateway like Paypal, the payments are deposited in your Paypal account. You should make sure that you have processed your order accurately, and we have a help document for that here. We also have an elaborate break down of the Shopify-Paypal setup here.
You may want to double-check that you've set up your Paypal correctly by checking out this guide.
If you've worked through all of this and still haven't received the payment, you may need to reach out to Paypal.
So to sum up:
1) Make sure you've processed the order correctly.
2) Make sure you've set up your Paypal correctly.
3) Failing that, reach out to Paypal.
All the best, Hyde.