Maybe try entering the password during that 1.5 minutes?

My thought process is that maybe it does print a prompt, but it does so while the boot process messages are going, and so the prompt just kindof gets lost somewhere in the scrollback buffer. But since it is (or rather if it is) waiting for input, it might work fine if you just enter the password.

If as you type, it doesn’t echo what you’re typing, I’d say that’s at least a bit of evidence that my hunch is right.

If that doesn’t do it for you, maybe share what distro you’re using, as well as the contents of your /etc/crypttab.