Great, thanks Rob.
For anyone else that will have this problem, I did get testing IAPs to work.
If you got your app downloaded using Test Flight for testing, then you are already set to test IAPs if you have them coded in your app. Your Test Flight account acts as a Sandbox account. Your IAPs can be in the “Ready to Submit” status, and I would connect them to your app in the “Prepare for Submission” area just to be safe. When you make a purchase with your Test Flight account, it does everything a normal purchase would do besides charge a fee.
You can, still, make sandbox accounts. Sign out of your iTunes account on your device, then open your test app and click on an IAP you wish to test. Sign in with your sandbox account. This allows you to test in other countries’ currency if you wish.
Hope everything works out for you,
Dan