managementUrl is nil in sandbox on ios

i have integrated RevenueCat Paywall ui in expo using the `react-native-purchases-ui` package. 
i’m trying to show the managment screen on expo dev client on my ios device after subscribing with test packages.

await Purchases.showManageSubscriptions()

but getting this error `ℹ️ managementURL is nil, opening Apple's subscription management page
 LOG  aa undefined`

i have checked the full setup quite a bit of times but couldn’t find any issue and also couldn’t get the relevant information from the docs as well. may be i’m mistaken, please point me to the correct direction if i missed something on the doc.

i have checked with 

await Purchases.getCustomerInfo()

✅ customer is there but customer -> `managementURL` is null. ❌

and by default it fallback to apple’s default management screen, which keep loading for few mins and later show connection error, try again.

just for more context, i have done these steps correctly.

Purchases.configure({ apiKey, appUserID  });

await Purchases.logIn(userId);