As I understand from the links below Samsung M20 is not supported by Knox Standard SDK.
https://www.samsungknox.com/en/knox-platform/supported-devices (does not listed here)
Programmatically, device does not produce any specific errors when trying to execute functions. Some give "Stub!" exceptions, some UNEXPECTED_ERRORs (kiosk mode result) etc. Btw, from what I gather from our logs, device can activate the API and run many functions without getting security exceptions. How should I test if a device supports Knox Standard SDK or not.
Edit: EnterpriseDeviceManager.getEnterpriseSdkVer() returns sth like "ENTERPRISE_SDK_VERSION_6.3"