In order to test my in-app purchases with iOS 13 I have to update one of my test devices to iOS 13.1 beta.
On iOS 12 and before there was a special Sandbox login in <
Sandbox Account section, in the iTunes & App Store of iOS 13, is not visible right away and can be confusing. Here is how to enable it:
You can't enter the sandbox account into iTunes & App Store as the primary account as of iOS 13 — the system will refuse to log you in with error with an odd copy mentioning "try again later." No matter how much you wait, iOS 13 will refuse your sandbox account here.
While unfortunately none of the suggested answers helped to actively bring back the Sandbox option, in my case it helped to update to the (now) latest iOS 13 version.
I do not know if this just a coincidence, if there was some bug fix in the latest iOS update or if I have performed any healing steps without knowing it...
So, while this is no real solution I added this answer just in case it might help someone else.
I had the same issue and i finally found the solution : You just try to purchase the product in your app and enter your sandbox user credentials then you will get the Settings/iTunes & App Store/Sandbox Account login.
It seems iOS bug, I had the same issue, And i was able to see SANDBOX ACCOUNT section only after doing these steps:
Afterwards you will be able to see your production apple id in use and the test apple id in SANDBOX ACCOUNT section.
Here's what worked for me (on a dedicated development iPhone 6s running iOS 13.3).
It took entering the credentials a couple of times, but the In App purchase dialog alert did say the environment was Sandbox.
After it "made good" (that is, stopped asking me to log in and processed the SKPaymentTransation), I was able to go to iTunes & App Stores in the General Settings, scrolled to the bottom, and now the Sandbox Account appears with the tester account showing.
Now when I run the app and click the button to purchase content, it just asks for the tester password.
Hopefully this helps others.
The following worked for me on ios 13:
Settings -> iTunes & App Store -> Scroll all the way down and click on "Sign In" under the "SANDBOX ACCOUNT" section