Empty layover-shadow mask

Hi, I’m using RTC to try and generate a layover-shadow mask, but the result is empty, i.e., all 0.
Source image: S1A_IW_SLC__1SDV_20230416T070255_20230416T070323_048118_05C8EC_E210 (Central Canary Islands, which are quite mountainous)

Pre-processing: Calibrate → Deburst

RTC settings:

The RTC op runs OK, here is the VV band produced:

The empty layover-shadow mask band:

There should be some layover and shadow values produced by this image, right?