This post shows you how to solve "Template parse errors: 'mat-form-field' is not a known element" in angular 7 when using the angular material.

Error throwing from your browser.

Uncaught Error: Template parse errors:
'mat-form-field' is not a known element:
1. If 'mat-form-field' is an Angular component, then verify that it is part of this module.
2. If 'mat-form-field' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.

You need to import MatFormFieldModule to your @NgModule

@NgModule({
  declarations: [
    AppComponent,
    ...
  ],
  imports: [
    MatFormFieldModule
    ...
  ]
  ...
})
export class AppModule { }

Next, try to add import CUSTOM_ELEMENTS_SCHEMA

import { CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';

then inject into @NgModule

@NgModule({
   ...
   schemas: [CUSTOM_ELEMENTS_SCHEMA]
 });

I hope so you can solve the problem 'mat-form-field' is not a known element in angular using angular material.