Error When Other Plugins Using OAuth Method Running

I have installed Super Socializer plugins: https://wordpress.org/plugins/super-socializer/

Both Super Socializer and Postman SMTP using OAuth 2.0, and sure i separated credential for each because there’s a different AUTHORIZED REDIRECT URI between Postman SMTP and Super Socializer

Now I found error every time new user register. After refreshed registration page, error not happened anymore.

I don’t know if this is may be related to SMTP PostMan plugins. But error occur when:

1. user finish social login registration (this is handle by Super Socializer) and after that process,

2. an email should be sent immediately to administrator to notify new user registration (this one handle by Postman SMTP).

Here are debug message:

Fatal error: Uncaught Error: Class 'Google_Utils_URITemplate' not found in /.../wp-content/plugins/super-socializer/library/Google/Http/REST.php:165 

Stack trace: #0 /.../wp-content/plugins/super-socializer/library/Google/Resource.php(191): Google_Http_REST::createRequestUri('gmail/v1/users/', '{userId}/messag...', Array) 

#1 /.../wp-content/plugins/post-smtp/Postman/Postman-Mail/google-api-client/vendor/google/apiclient-services/src/Google/Service/Gmail/Resource/UsersMessages.php(197): Google_Service_Resource->call('send', Array, 'Google_Service_...') 

#2 /.../wp-content/plugins/post-smtp/Postman/Postman-Mail/PostmanGmailApiModuleZendMailTransport.php(200): Google_Service_Gmail_Resource_UsersMessages->send('me', Object(Google_Service_Gmail_Message), Array) 

#3 /.../wp-content/plugins/post-smtp/Postman/Postman-Mail/Zend-1.12.10/Mail/T in /.../wp-content/plugins/super-socializer/library/Google/Http/REST.php on line 165

Error only happen at that process, otherwise everything goes normal both Postman SMTP or Super Socializer.