[Vuejs]-Undefined variable on production setup, correct value on development

When using Composition API, e.g. using things like ref, and setup() or <script setup> tag, that API syntax does not use the keyword this when referencing other variables or functions. It should throw errors even in a dev environment, not sure why yours isn’t. Regardless, removing this and using proper Composition API syntax throughout, e.g. email.value should fix the issue.