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Check if your component is added in declarations in app.module.ts
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You are using an odd mix of template driven and model driven form.
Choose either and do not mix those two.
No need to set required or minlength in template, we handle thid in the component.
Also we do not need any ngModel, name etc, since we use formControlName.
Also remove #f="ngForm" as that is related to template-driven form.
use #prof="ngModel" OR [(ngModel)]="prof" ( just one )
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Check that you have imported the component itself for which you are trying to use the form.