Page expired when submitting form - laravel

Question

I am using a modal, and when opens the modal then close it, then open it again to add user, it says page expired upon submitting.
here is the my modal with my form
<div class="modal fade" wire:ignore.self id="studentModal" tabindex="-1" aria-labelledby="exampleModalLabel" aria-hidden="true">
<div class="modal-dialog modal-xl">
<div class="modal-content">
<div class="modal-header">
<h5 class="modal-title" id="exampleModalLabel">Patient Registration</h5>
#if(Session::has('message'))
<p class="alert {{ Session::get('alert-class', 'alert-info') }}">{{
Session::get('message') }}</p>
#endif
<button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close" id="closeReset1" onclick="resetInput()"></button>
</div>
<!-- START FORM -->
<form action="add" method="POST">
#csrf
<!-- START MODAL BODY -->
<div class="modal-body">
</div>
<div class="modal-footer"
</div>
</form>
</div>
</div>
here is my route
Route::post('/add', [App\Http\Livewire\UHispatients::class, 'savePatient'])->name('registerPatient');

Answer 1

if you are using the naming route and check your model fillable
<form action="{{route('registerPatient')}}" method="POST">
#csrf
<!-- START MODAL BODY -->
<div class="modal-body">
</div>
<div class="modal-footer"
</div>
<button type="submit">submit</button>
</form>

Answer 2

As I can see, you just forgot to put action for your form in your modal.
If you submit using the submit button, then your problem is using the route path "add" instead of using the route path or route name.So as your route has name you can use it like this :
<form action="{{route('registerPatient')}}" method="POST">
#csrf
<!-- START MODAL BODY -->
<div class="modal-body">
</div>
<div class="modal-footer"
</div>
<button type="submit">submit</button>
</form>
If you're submitting your form with Ajax, then the csrf tag should be sending with your Ajax request. So, your Ajax header should be like this :
<script type="text/javascript">
$('#YOUR_FORM_ID').on('submit',function(e){
e.preventDefault();
let name = $('#name').val();
$.ajax({
url: "{{route('registerPatient')}}",
type:"POST",
data:{
"_token": "{{ csrf_token() }}",
name:name,
},
success:function(response){
console.log(response);
},
error: function(response) {
console.log(response);
}
});
});
</script>