Angular 2: formGroup expects a FormGroup instance. Please pass one in

Your patientForm is undefined until the patient in the subscription is populated. As such, you're trying to bind to a value that doesn't exist in the template at the time the template is parsed.

Add an *ngIf to render the form only when patient is truthy, or the form group is instantiated:

<section class="CreatePatient">
    <form *ngIf="patient" [formGroup]="patientForm" (ngSubmit)="onSubmit()">
        <div class="row">
            <div class="form-group col-12 col-lg-3">
                <label for="firstName">First Name</label>
                <input formControlName="firstName" type="text" class="form-control" id="firstName" >
            </div>

        <div class="row">
            <div class="col-12 col-lg-2">
                <button type="submit" name="submit" class="btn btn-block btn-primary">Save</button>
            </div>
        </div>
    </form>
</section>

When the patient is populated in the subscription, the patientForm instance will exist and the binding will work. It's a common "gotcha" when dealing with async values.

Forms don't always have starting values, so you can also check for the existence of the form itself:

<form *ngIf="patientForm" [formGroup]="patientForm" (ngSubmit)="onSubmit()">

The important part is that the form isn't rendered until its instantiated.

Guys who face issues with reactive forms First in your component.ts file make sure you import the following:

import { FormBuilder, FormControl, FormGroup, Validators} from '@angular/forms';

export class NewsfeedformComponent implements OnInit {

NewsfeedForm: FormGroup;
constructor(private _formBuilder: FormBuilder){}

 ngOnInit() {

this.lookupService.getStatus().subscribe((status: IStatus) => {
  this.status = status;
});

this.NewsfeedForm = this._formBuilder.group({
  NewsfeedID: [0,null],
  StatusID: ['', Validators.required],
  publishdate: ['', Validators.required]
  })
 }

}

in your component html file

             <form class="form-container" [formGroup]="NewsfeedForm" 
#newsFeedform="ngForm" (ngSubmit)="form1()">

 <div id="rowTwo" fxLayout="row" fxLayout.lt-md="column" fxLayoutGap="20px" fxLayoutGap.lt-md="0px">
                <mat-form-field appearance="outline">
                    <mat-label>Status</mat-label>
                    <mat-select formControlName="StatusID" required>
                        <mat-option></mat-option>
                        <mat-option *ngFor="let itemofStatus of status" [value]="itemofStatus.StatusID">
                            {{itemofStatus.Status}}
                        </mat-option>
                    </mat-select>
                </mat-form-field>

                <mat-form-field appearance="outline">
                    <input matInput [matDatepicker]="publishdate" placeholder="Publish Date"
                        formControlName="publishdate">
                    <mat-datepicker-toggle matSuffix [for]="publishdate"></mat-datepicker-toggle>
                    <mat-datepicker #publishdate></mat-datepicker>
                </mat-form-field>
            </div>

Problem is that your form is null on the beginning.

And only on ng init you will get patient and then create it. You should initialize your form on the begining or

<section class="CreatePatient" *ngIf="patientForm">