Unity not letting me download assets/ giving me error : unable to open this helper application for com.unity3d.kharma:content/13866

I am having a huge problem downloading assets from the unity asset store. When I sign in and go to download an asset by clicking on the open in unity button it gives me an error

• unable to open this helper application for com.unity3d.kharma:content/13866 the protocol specified in this address is not valid. make sure the address is correct, and try again. -

I recently had two versions of unity. Unity 4.0 which the assets that I was downloading had to be a higher unity so I deleted that unity 4.0 leaving my unity 5.0 as the only one. Now I can't download the assets. Why won't the assets download to 5.0? Both unity 4.0 and 5.0 were on the same account.