iPhone In-App Purchase Store Kit Error -1003 "Cannot Connect to Itunes Store"

Cannot connect to iTunes Store in-app purchases

Make sure you have signed out of any production iTunes accounts on the device.

I was getting this error on my test phone which was logged in with my actual iTunes account. You cannot test apps using your production iTunes account, hence the error. I just wish Apple provided a better error so as to avoid this guesswork...

InApp Plan change always gives Cannot connect to iTunes store error

Finally i have solved this case with a workaround. Even if we got the error or not the receipt will be available, try to validate the receipt. If the subscription plan changed it will get in receipt validation. Don't need to consider the "buyProduct" failed state. No need to display the error just we can try receipt validation if that also failed then the purchase is not done actually.

store kit transaction error: Cannot connect to iTunes Store on ios 7 device

I had the same issue. Here is similar question I am getting error while requesting products from App Store for IAP

Try doing this:

1)You have to test on device

2)Go to setting -> iTunes & App Store -> and log out of your account.

Remove app from device and clean all data.

Make sure you have done all necessary steps for in-App purchase testing. Here is apple
documentation

Run on device and test it.

Cannot connect to iTunes Store with newly created sandbox tester

After a lot of searching, I was able to find the answer online:

https://forums.developer.apple.com/thread/90594
It was posted by: neilc

This is what worked for me in the end:

-Create a new iTunes Sandbox user. Do NOT verify the email address.

-Sign out of the App Store on your device.

-Begin your purchase flow.

-When prompted, tap Use Existing Account.

-Login with your new Sandbox user.

-You will be prompted to log in again—DON'T! I cannot stress that enough.

-Hit Cancel.

-Background the app.

-Foreground the app.

-Begin your purchase flow again.

-This time, you will be prompted for your Sandbox user's password (the email address will be shown in the prompt).

-Enter your password.

-Continue through the In-App Purchase flow. Purchases will succeed this time around.

If you check your App Store settings on your device, you will notice the Sandbox user is logged in. DO NOT SIGN OUT or you will invalid the Sandbox user and you will have to repeat the above steps from the beginning.

tvOS - In app purchase throws Cannot connect to iTunes Store error

I manage to solve the issue with Signing out from iTunes account in Settings->Accounts-> iTunes and Appstore and then the app asked me for credentials and I entered the test credentials. Everything works fine.

PS. Do not use NSUserDefault for saving the purchase result as I did on the sample code. This was a testing code and NSUserDefault won't work as expected(iOS)

IAP - Cannot connect to iTunes Store - only during apple review

Just an update, after a while, after a few ping-pong with review team, it got accepted, and since that, it works fine (also for review team during app updates).
Probably some internal issues they had.