There are two steps to registering a System App.
- First, create a System Account
- Second, Register a System App using the above System Account
In you case, you completed the first step of registering a System Account and got an Account with SystemAccount ID: f58a******
In the second step, you registered the System App but not with SystemAccount ID: f58a******. Instead you used the ID: 9e2f84ba-568a-e9a6-4dfb-b6413ee595a8 which does not correspond to a System App, and hence the failure.
To make the App work correctly, you need to register a new System App and when asked to input the GUID, enter f58a******
Once done, while testing used the credentials from SystemAccount ID: f58a******