APAC firmware 14.20 problem - DEM from OpenStreetMap not working in calibration of altitude

I have an APAC version of Descent MK2i.

I am currently in UK. Due to lack of maps in UK, I have to import maps from OpenStreetMap.

However, it shows no DEM data when I calibrate the altitude with DEM since I have updated it to firmware 14.20.

I have tried to download various maps from different sources. Nothing works so far.

Am I missing something here?