Known issue. Some people have had success logging out and back in, some have not.
What to do in Sirius as KDF - Well, there are several DOFF missions there and you gain access to the DV cluster to do the DOFF missions there as well.
Other than that, I use to to get to Cardassian space without having to go through EE-Orellius. You can also use the Fed TW gate to get to Borg space (theirs is fixed, so it takes you to GO instead of BGO).
I actually posted a bug report about this when I gained the rank some time ago. On closer inspection I ralised the tooltip for rank four does not actually say that you should. Admittedly all the others do grant one but this one doesn;t claim to. On reflection maybe it is unfair, but it cannot be described as a bug.