# Authentication Service Provider Interface not found

**URL:** <https://discourse.cakephp.org/t/authentication-service-provider-interface-not-found/8687>\
**Category:** Need Help\
**Created:** [December 2, 2020, 7:29pm UTC](https://discourse.cakephp.org/t/authentication-service-provider-interface-not-found/8687 "2020-12-02T19:29:59Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![fedemarino75](https://avatars.discourse-cdn.com/v4/letter/f/6a8cbe/32.png) [@fedemarino75](https://discourse.cakephp.org/u/fedemarino75)\
**Post date:** [December 2, 2020, 7:29pm UTC](https://discourse.cakephp.org/t/authentication-service-provider-interface-not-found/8687/1 "2020-12-02T19:29:59Z")

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Hi, I’m trying to install Authentication Plugin on cakephp 3.9 app  
I followed the steps in  
[https://book.cakephp.org/authentication/1/en/index.html](https://book.cakephp.org/authentication/1/en/index.html)  
I installed the plugin using composer and modified Application.php and AppController.php

But I getting the following error

Fatal error: Interface ‘Authentication\AuthenticationServiceProviderInterface’ not found in

I added the following lines at the begining of Application.php

> ```
> use Authentication\AuthenticationService;
> use Authentication\AuthenticationServiceProviderInterface;
> use Authentication\Middleware\AuthenticationMiddleware;
> use Psr\Http\Message\ResponseInterface;
> use Psr\Http\Message\ServerRequestInterface;
> 
> ```

My cakephp installation is up to date. What could be wrong?  
Where should I check if the source file for AuthenticationServiceProviderInterface exists?

Thanks

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<div class="post-metadata">

**Author:** ![fedemarino75](https://avatars.discourse-cdn.com/v4/letter/f/6a8cbe/32.png) [@fedemarino75](https://discourse.cakephp.org/u/fedemarino75)\
**Post date:** [December 4, 2020, 12:44pm UTC](https://discourse.cakephp.org/t/authentication-service-provider-interface-not-found/8687/2 "2020-12-04T12:44:46Z")

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I solved the issue, it was a silly mistake.  
I had installed the plugin on the wrong folder

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**Author:** ![pjs](https://avatars.discourse-cdn.com/v4/letter/p/ad7895/32.png) [@pjs](https://discourse.cakephp.org/u/pjs)\
**Post date:** [April 20, 2021, 4:54pm UTC](https://discourse.cakephp.org/t/authentication-service-provider-interface-not-found/8687/3 "2021-04-20T16:54:32Z")

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please can you tell me how you solved it?? Im facing the same problem