Nuget v3 proxy not redirecting to https through Reverse Proxy IIS

I have set up a Nexus Client which runs behind a reverse proxy redirecting http traffic to https. The reverse proxy is configured with IIS follwoing this guide:

How to Configure IIS as a Reverse Proxy for Sonatype Products – Sonatype Support

I have a nuget v3 proxy repository that points to https://api.nuget.org/v3/index.json. The same one that is created by default when setting up Nexus Client for the first time.

Whenever I try to access the index.json for performing an installation or search it is always accessed through http:

C:\nuget>nuget install newtonsoft.json -Source https://example.com/repository/nuget.org-proxy/index.json
Feeds used:
  https://example.com/repository/nuget.org-proxy/index.json
Installing package 'newtonsoft.json' to 'C:\nuget'.
 GET http://example.com/repository/nuget.org-proxy/v3/registration/5/newtonsoft.json/index.json
An error was encountered when fetching 'GET http://example.com/repository/nuget.org-proxy/v3/registration/5/newtonsoft.json/index.json'. The request will now be retried.

However using a nuget v2 proxy that point to https://www.nuget.org/api/v2 works:

C:\nuget>nuget install newtonsoft.json -source https://example.com/repository/nuget.org-v2-proxy/
Feeds used:
  https://example.com/repository/nuget.org-v2-proxy/

Installing package 'newtonsoft.json' to 'C:\nuget'.
  GET https://example.com/repository/nuget.org-v2-proxy/FindPackagesById()?id='newtonsoft.json'&semVerLevel=2.0.0
  OK https://example.com/repository/nuget.org-v2-proxy/FindPackagesById()?id='newtonsoft.json'&semVerLevel=2.0.0 3030ms
  GET http://example.com/repository/nuget.org-v2-proxy/FindPackagesById()?semVerLevel=2.0.0&$skip=40&id=%27newtonsoft.json

What could be the issue here?

You need to configure IIS to send the correct X_FORWARDED_PROTO header. See here:

Rich