Checking if model has changed by other user

I have a Post model and an edit.blade to change the status on this. If two users updates the status simultanously I want the latest to fail. I though I could use isClean()/isDirty() for this but it seems like this only works withing the current request cycle, which I guess means for the same user session. So I am now trying to check if there is a newer update on the same record.

The the form to update the status looks like this:

<form method="POST" action="{{ route('selvbetjentUpdate', $post) }}">
    @csrf
    <th class="py-4 px-6"> Status <br/> ("Code sent"=>send mail)</th>
    <td class="py-4 px-6">
        <div class="mt-1 border rounded-lg">
            @foreach ($statuses = App\Models\ResponseStatus::where('request_type_id', 1)->get() as $status)
                <input id="{{ $status->id }}" type="radio" name="status" value="{{ $status->id }}" {{($post->responseStatus->description==$status->description) ? 'checked' : ''}}/>
                    <label for="{{ $status->id }}">{{$status->description}}</label><br>
            @endforeach
        </div>
    <tr>
        <th class="py-4 px-6"> &nbsp </th>
        <td>
            <x-jet-button class="ml-4">
                {{ __('Sett status / send mail') }}
            </x-jet-button>
        </td>
    </tr>
</form>
	

My controller update method looks like this:

public function update(CustDeliveryPost $post)
{
    $id=request()->input('status');
    $kode=request()->input('code');
    $latestPost=CustDeliveryPost::where('id', $post->id)->first();
    if ($latestPost->updated_at == $post->updated_at) { // WHY IS NOT THIS WORKING?
        $post->response_status_id=$id;
        $post->save();
        if ($id==2) { //status="code sent"
            $reply=new SelfserviceReply($kode, $container);
            $reply->subject('Code... ');
            Mail::to($post->epost)->send($svar);
        }
        return view('/custdeliveryposts.update', ['id', $post->id]);
    }
    else { // Someone else changed the status before you
        return view('/custdeliveryposts.updateFail');
    }
}

Why doesn't my if statement to check if record was altered after read work: if ($latestPost->updated_at == $post->updated_at)?