Actually I think I figured it out. It seems this application has a hard time if you add subnets too fast (i.e. adding more while currently scanning one). I added all these subnets quickly.
Now that I rescan them one at a time, they start showing actual hosts (where it says all IPs available before) and now it turned green.
I guess the question now is, is this tool not multithreaded? Can it only scan one subnet at a time?
Also, on some of these subnets I distinctly remember seeing hosts populating into the grid during the initial scan I did whereas today when I rechecked, all IPs were listed as available until rescanning. This is slightly problematic.
Sorry for the delayed response. IPAM will scan 2 subnets concurrently.