I recently secured one of my web services with HTTPS and when I tried to add the service to a MonoTouch project nothing happened. The screen looked like it was adding it but it didn’t finish I just had to cancel it.

It’s all down to trust and certificates. I opened a Terminal session on my Mac (Applications > Utilities > double click Terminal) and typed the following:

mozroots --import --sync

Then closed MonoTouch and reopened. Then I was able to add in the secure web service.