Web Request to Rest EndPoint - Specified value has invalid non-ASCII characters. Parameter name: name

I am trying to activate a feature using the rest api within SP 2013..

I can  get the form digest from the site without issue however, when i try to post using web request i receive this error:

Parameter name: name

There is no payload within the message, everything is encoded within the url. I have tried the same call using another rest client, and it works without issue. The only thing i can guess is that somehow the values are being encoded randomly before being sent to the endpoint without me realising.