Frame and focus not changing with DSLR

I recently got a Canon 6D and am trying to get it working with SGP. The only thing that is giving me trouble is using the Frame and Focus to help decide what exposure time I want.

On my ZWO camera, I’m used to setting my gain level and then just picking different exposure times, taking a shot with Frame and focus, and looking at the image stats to see what I end up with. With the DSLR, I set the ISO and take a shot, and everything works. When I change the exposure time (60 seconds to 90 seconds) the image shown is still the same one as before. The only way I get a new image is to change the ISO before the next test shot.

Anyone know what’s going on here? Is there some setting that I’m missing? When running an actual sequence, things seem to capture fine. Thanks!