Freeze not working - disabling track

Can anyone help me with enabling the “Freeze” snowflake button on each track in Cubase? I’m working with a template for a series I’m writing for, and I’m trying to make ti a little faster to open my sessions, as well as export audio mixdowns by “purging” or freezing some tracks that are not currently in needed. Am I going about it the wrong way or is there some way I need to enable this Freeze button?

Thank you!