Not able to generate 3sm from DTM + Aerial Photos

Hi, Dear All,

I tried several times to generate a 3sm file from a dtm terrain and aerial photos. However, I only get an all-white 3sm model (see below). Could you please help me solve this?

I felt it is because the GCSs of the dtm and aerial photos are not matching. But when I refer them in, they actually match. I am just clueless now. Please advise.

Thanks!