Hi Jagan CR ,
Thanks for your comment!
Yes, this has been a recent design change. The Azure Portal has been upgraded to use API Version 2019-12-01.
With this change, APIM users having the 'API Management Service Reader Role' would no longer be able to read subscription keys. Neither would the subscription keys be automatically added while performing sample API calls from within the Test console of the APIM service for users having this role (Users with the ‘API Management Service Reader Role’ would have to manually provide the subscription key).
This change has been documented in the following article and would also be updated in APIM update/release notes shortly.
https://github.com/Azure/azure-sdk-for-net/blob/master/sdk/apimanagement/Microsoft.Azure.Management.ApiManagement/CHANGELOG.md
The blog has also been updated to reflect this new change.
Thank you!