Hi @cstekelenburg_4169 ,
If you created a connector with the proper URL, username, and password, then you've set it up correctly.
Please note, you will not be able to list or search remote packages in the ProGet UI. This is a limitation, since ADO is rudimentary and does not support listing/searching.
Instead, you will need to use the NuGet API (Visual Studio, Nuget.exe) to pull packages. Once package has been pulled through ProGet, you will "see it" in the UI since it's been cached.
I'm not trying to be pedantic with terminology, but please note it's not a "sync" -- it's more of a "proxy" or "pass through". When you make a request via the NuGet API, that API request is forwarded to your connector (I.e. Azure DevOps).
-- Dean