To access SQL Inventory Manager over HTTPS with a self signed certificate you may need to enable SSL on SQL Inventory Manager 2.6 REST service, and add a certificate.
For information on how to create a self signed certificate for Dashboard refer to Resolving+the+certificate+error+message
Using a self-signed certificate
Using a self-signed certificate only works with both IDERA Dashboard and SQL Inventory Manager installed on a local machine.
Binding a self signed certificate to
To add a certificate to the Trusted Root Certification Authorities store in Windows, refer to Manage Trusted Root Certificates.