Hi, sorry I don't was use the Settings -> App Store -> Account Sandbox but I just was use the principal iCloud account. In any case even if I use the main account and the OS recognizes that is a test account this should not prevent me from authenticating with other test accounts. However now that I have blocked the maximum number of main accounts if I want to transfer this phone to a friend or one of my family, or sell it, what can I do to solve it ? thanks Danilo

I have the same issue and I still haven't found a solution