App Store error: NSURLEddorDomain error -1012 on El Capitan

Hi,

I successfully updated my Macbook Pro (late 2012) to El Capitan, but now I can't check for updates in the App Store.

I get the following error message:

An Error has occurred.

The operation couldn't be completed.

(NSURLErrorDomain error -1012).

I can't find any relevant info on this anywhere....