Template parse errors:
‘app-input-button-unit' is not a known element:
1. If ‘app-input-button-unit' is an Angular
component, then verify that it is part of this
module.
2. If ‘app-input-button-unit' is a Web
Component then add 'CUSTOM_ELEMENTS_SCHEMA' to
the '@NgModule.schemas' of this component to
suppress this message. ("
</h1>
[ERROR ->]<app-input-button-unit></app-input-
button-unit>
✅ solution
In older versions of Angular you need to put your components in that case to the declerations of angular module.