Hey, @lauren87👋 Thanks for your question. You'll need to have your super admin or your dev update the template to include the payment schedule feature into your custom quote template. My guess is that this is a custom quote template that was created before the payment schedule feature being released last year — payment schedule announcement.
If you have access to the Design Manager, you can view an example of how this module is implemented (screenshot) Design Manager > cms-quotes-theme > templates > basic.html and search(cmd-f on Mac) for payment schedule
I have removed all mentions of payment schedule on all of the templates including the one with the error but the error still exists. The code for payment schedules wasn't in my template but error still occurs. I am a developer and have full knowledge of hs but wondering if this is a bug?