hi,
This behavior (Native app calling a microflow from a nanoflow and getting an Internal Server Error with no logs) is a known issue in Mendix Runtime version 9.24.41. It happens because of a regression in how Native client requests are handled by the runtime in that patch level.
You are not doing anything wrong in your microflows or security settings.
Upgrade the runtime to a patch version where this is fixed, such as:
9.24.42 or later
OR upgrade to:
10.x
This specific regression was fixed in later maintenance releases of 9.24.x and is not present in those versions.
Upgrading resolves the issue instantly without code changes.
If you cannot upgrade immediately:
But this is only a workaround — the real fix is upgrading the Mendix runtime.
No model, security, or microflow changes are needed — just update the runtime.