I had this issue back in Nov 2013. It seemed that it was at the server side.
If you make a request through a proxy you get a 400 Invalid URI response.
If you don't use a proxy, you get a 200 OK.
Looks like it's still the same.
A proxy style HTTP request:
openssl s_client -connect activate.f5.com:443
...certs etc...
---
HEAD https://activate.f5.com/license/services/urn:com.f5.license.v5b.ActivationService HTTP/1.1
SOAPAction: ""
Host: activate.f5.com
Connection: close
HTTP/1.1 400 Invalid URI
Date: Tue, 30 Dec 2014 11:42:54 GMT
Connection: close
...
A non-proxy style HTTP request:
openssl s_client -connect activate.f5.com:443
...certs etc...
---
HEAD /license/services/urn:com.f5.license.v5b.ActivationService HTTP/1.1
SOAPAction: ""
Host: activate.f5.com
Connection: close
HTTP/1.1 200 OK
Date: Tue, 30 Dec 2014 11:43:48 GMT
Content-Length: 179
Content-Type: text/html; charset=UTF-8
...
I just used HEAD because it's easier to manually debug it that way.
One for F5 I guess. I'll try and open another support ticket.
You may be able to get around it if you can use transparent proxies, but it
really does need fixing at the server side.