DRM (digital rights management)

Can DRM be added to apps made using MIT app inventor?

Encryption is possible and relatively easy. Other forms of DRM might not be practical. What might be possible depends on what you intend to restrict as a capability of you app.

I received this error

Where are you trying to upload your app?

Amazon Appstore

Then please take up your issue with Amazon.

Also, search the community for others who have had the same issue, they may have a solution...