Development team active in Slack, but also needs communication in the Bitcointalk Forum, there are more members here.
I'm not on Slack, what do you mean by "active"? Still no activity on their github account at
https://github.com/siriuscore/sirius , for 6 months now, except some tiny cosmetic changes 11 days ago. As predicted, I think this coin is dead, with the price now much less than half when it was listed on Cryptopia, and last daily trading volume of 0.07 BTC per day. It is like penny stocks now.
Relax, currently all coin is down many people doing sell move, just looking on CMC. And unfortunately, sirx listed on market when all coin while down trend. that's why many people not only you will thinking "ahh it seems sirx has no chance to raise up the price again i think this coin will dead soon", this is all just beginning no need to hurry, at least this coin is only from airdrop no ico so please to everyone dont blame sirx if the price go down. try find the good moment to buyback if you still want to support sirx.
The easiest way for a supposed promising project to die faster than usual is when there are too many unnecessary silence and inactivity mostly in the part of the core devs,
An activeydev team is first important part of project before the backing of a supportive community, if they don't give update for days weeks certainly it will not look good on the progress of the project,
A lot of members have already pointed out the lack of communication of devs here, still no changes whatsoever. Hope things turn around.