Zapomněli jste uvést $client->cn_id<option value='{{$client->cn_id}}'>{{$client->cv_name}}</option>;
Totéž zde:<option value='{{$invoice->cn_id}}'>{{$invoice->cv_method}}</option>;
Zapomněli jste uvést $client->cn_id<option value='{{$client->cn_id}}'>{{$client->cv_name}}</option>;
Totéž zde:<option value='{{$invoice->cn_id}}'>{{$invoice->cv_method}}</option>;