You should make sure which steps block the process. You can watch it in the sending request event.
For WfsFeatureSource it have two events: RequestingData and RequestedData, you can also try to watch that.
When you open the layer, it will call GetColumns.
In fact I am not so familiar with WFS standard, but it looks we have these API can be overrided, you can override each of them and add break point to locate where is the problem.
Wish that's helpful.