This blog article describes how you can activate debugging for the Licensing page plugin.

 The article is relevant if you get the following error message although this setting exists. The message below can appear on the licensing tab of the web configuration. 

Figure 1: Error message

First, you have to enable tracing for your organization: Open a browser and navigate to Dynamics 365 -> Settings -> Administration -> System Settings -> [Customization]-tab and select "All" from the drop-down menu of the Enable logging to plug-in trace log. 

Next, go to Dynamics 365 -> Settings -> Products and check if a record named "Plugin" already exists. If not create a new one by hitting the "NEW" button.
Name: Plugin
Product Type: server

In the subgrid in its body ensure that a Settings Key with the following information exists:
Name: debug
KeyValue: true

The result will look like in the figure below: 

Next, reload the licensing page to generate log files. 

Then access the log files: Dynamics 365 -> Settings -> Plug-In Trace Log and look for "PTM.Plugins.CheckLicense.CheckLicensePlugin". 

Finally please send us the content of the "Message Block" field. 

That’s it! We appreciate your feedback! Please share your thoughts by sending an email to support@mscrm-addons.com.