Could be related to trying to run it on a realm rather than a normal server. Cause the command doesn't want to show up in chat on the realm for some reason.

your running calcmod on your client?

yes

Unfortunately, I do not have a realm so I can't really test but do other mods work on your realm? And do you have like a log you could upload from your client?

It has been tested on realms now and confirmed working. I'm closing this issue for now, but if you have further troubles comment again.