this issue is related to admin created user access. it is occurs if user try to access unauthorised resources i suggest you to do the following two things
check your acl.xml file and provide access to the resource from backend using administrator credencials navigate to system>>user roles>>resources and checked the recource option @) remove/comment the _isAllowed() method body from controller file. like below.
protected function _isAllowed() { return $this->_authorization->isAllowed('Webkul_Hello::employee'); }