1. If 'mat-form-field' is an Angular component, then verify that it is part of this module. code example
Example: 'mat-form-field' is not a known element
@NgModule({
imports: [
...
MatFormFieldModule,
MatInputModule,
...
]
})
@NgModule({
imports: [
...
MatFormFieldModule,
MatInputModule,
...
]
})