Prism projects in Rider

Hi,

with Rider now beeing free for non-commercial use I installed it today (so happy about that), but unfortunately I cannot successfully build my Prism WPF project in Rider. In the App.xaml.cs I get “Cannot resolve symbol xxx” in my usings, even though the packages are installed (it's working with VS): 
DryIoc
DryIoc.Microsoft.DependencyInjection
Microsoft.Extensions.DependencyInjection
Microsoft.Extensions.Logging
NLog.Extensions.Logging
Prism.DryIoc
Prism.Ioc
Prism.Modularity

What can I do about it? I don't want to continue with VS now that Rider is free…

PS: The project was created a few years ago using the Prism pject template pack.