Drill down to Dynamics NAV 2016

One of my customers wants to connect Dynamics 365 CE with their existing NAV environment 2016.
For this, I installend "DynamicsNAVIntegrationSolution" and the Integration for accounts and contacts works fine, including the NAV Statistics in CRM. I just can't get the "Dynamics NAV" button on the account page. Someone an idea, what steps I have to do for this.

Regards,
Hilde