Hi Daniel,
I hope you are doing great.
By default, the 2M PHY is not enabled. Please define gBleUseHSClock2MbpsPhy_c as 1 in the app_preinclude.h file
/* Enable HS Clock to support 2Mbps PHY mode setting */
#define gBleUseHSClock2MbpsPhy_c 1
Regards,
Mario