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You can then test the authentication and attribute mappings by browsing to https://engine.govconext.nl/authentication/sp/debug  

Allow users 

Please ensure that in Azure AD you assign users and groups to this ‘Enterprise application’ > ‘govconext’ through the menu-item ‘Users and Groups’ on the left. 

This step is often forgotten and the result is that users cannot log in. 

Troubleshooting 

Govconext provides a debug page that shows which attributes are received and other useful information:
https://engine.govconext.nl/authentication/sp/debug 

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