Android 9 has a limitation such that every application can scan the Wifi environment only four times in two minutes. As a consequence

• Using MapCreator with Android 9 is not recommended. 
• Instead, the suggested solution is to use a device with Android 8 or Android 10 for fingerprinting.
• Enable BLE (or BLE background scanning) in the app you are developing to guarantee good performance on Android 9 as well.

Note that MapCreator automatically warns you with the built-in warnings, if Wifi or BLE scans are not received with reasonable frequency.

Note also that since IndoorAtlas positioning fuses geomagnetic, PDR, BLE and barometric information in addition to using Wifi, the positioning quality is not severely affected by this limitation.

Please see supported devices list.