Restricted ports from ISP

> I've recently upgraded to the N600 [...]

   Not the model number.  From what?

> Model: C3700|N600 Cable Gateway Docsis 3.0

   Is that accurate?  Firmware version?

> [...] now my wireless security camera [...]

   Not a very detailed description of anything.

> [...] keeps going offline.

   "offline"?  Determined how, exactly?  As usual, showing actual
actions with their actual results (error messages, LED indicators, ...)
can be more helpful than vague descriptions or interpretations.

   Are you trying to access your (unspecified) "my wireless security
camera" from a system within your LAN, or from somewhere in the outside
world?  How, exactly?

> Manufacturer is asking me to verify that your ISP is not restricting
> ports 80 and 554 on your network.
> How do I do this?

   Call your ISP and ask?  It might help if someone in the conversation
had some idea of what your (unspecified) "my wireless security camera"
actually requires in the way of connectivity. Is it trying to reach
some external web server at port 80, or is it running a web server which
listens at port 80, and must be accessible from the outside world?

   Port 554 suggests something involving RTSP, but how it's used remains
a mystery:

      https://wiki.wireshark.org/RTSP

   Are you using UPnP or port forwarding on your (modem+)router?