When trying to publish an app file on sandbox I get this error (see picture) :
External Deployment is not enabled. Please contact your system administrator.
If you are running on BC Saas, it is not possible to allow internal development.
If you are running on your own enviroment then go to the NST and change the allowed setting:
For help, do not use PM, use forum instead, perhaps other people have the same question, or better answers.
Answers
If you are running on your own enviroment then go to the NST and change the allowed setting: