No IP address.....can I fix this?

Next time Comcast comes to do something like that, tell them to put their device is pass-through mode so it doesn't mess with your network.  If the tech says he can't do that, he's just poorly trained -- have him call his supervisor.  I had a cable guy who set mine up as double-NAT, though I didn't realize it at first.  After realizing what he'd done, I got through the first level of phone support and convinced the real tech I knew what I was doing, and he walked me through how to put their router into pass-through mode (so it simply acts like a modem).  Oh, and then make sure they aren't charging you for a router you aren't using as one.  My cable company advertises a "free modem" with internet service, which does not mean "free router".  Then, conveniently (for them), none of the tech's carry simple modems in their trucks.  They scan in the router, and it's added to your monthly bill.  It took another call and second-level support to get that removed from my bill.

What I'm sure you ran into is that you previously put your NAS into static IP mode to reserve an address.  That's not the best way to do it, precisely for instances like this.  It is much better to make a reservation in the router.  Glad you found a solution.  This info is more for anyone else finding this and looking for an answer to a similar problem.