juste dowloaded the demo of max 8 - in order to run my max 7 I renamed it as Max7, as it is said soemwhere. Then opening REAKTOR as a vst (in a patch which works since more than one year, was often played etc etc) Max console (of max 7) says there is no Reaktor VST - same for the AU (I work on MAC) version... However the Reaktor vst and AU open just fine in max8 (I renamed max 8 as Max8) - which is not even in demo mode (no save) but is "runtime".
Renaming my Max7 as Max solved the problem. But are you sure the 2 can coexist on the same computer ?
mac, os Sierra, max 7 and max8 demo