Added switch to network but not working

> My internet provider has given me a Homehub 3000 MODEM ROUTER. [...]

   Is it configured as a modem+router, or as a modem only?

> [...] 1 OF 4 ports is connected to my netgear nighthawk R7200 AC2100
> smart wifi router. [...]

   So, is that a modem-only with the R7200 as a router (ok), or a
modem+router with the R7200 as a router (less than ok)?

> [...] I bought a Netgear prosafe 24 port gigabit switch JGS5524, [...]

   "JGS524"?  Plain-old "JGS524[v1]", or some newer/fancier variation?
Look for "Model" on the product label.

> Model: JGS524v2|ProSAFE 24 Port Gigabit Rackmount Switch

   Which/what is it, really?

> [...] PLUGGED it into the 2nd port of the primary netgear router [...]

   Do you mean that you ran an Ethernet cable from the R7200 LAN port 2
to some port on the JGS524?

> [...] but it's not working.

   Which kind of "not working"?

   A vague description of what some device does _not_ do is less useful
than a clear description of what _does_ happen.

   "not working" is not a useful problem description. It does not say
what you did.  It does not say what happened when you did it.  As usual,
showing actual actions (commands) with their actual results (error
messages, LED indicators, ...) can be more helpful than vague
descriptions or interpretations.

   Have you tested/swapped the Ethernet cable(s)?

> Any idea as to the possible problem? [...]

   Without knowing what the LED indicators indicate?  Not with my weak
psychic powers.

   Visit http://netgear.com/support , put in your model number(s), and
look for Documentation.  Get the User Manual (at least).  Read.  Look
for the LED descriptions and "Troubleshoot".