Three Nighthawk R7000 routers aren't working

> Model: R7000|AC1900 Smart WIFI Router

   Firmware version?  What, exactly, did you connect to what, exactly?
(Hint: If a device has different types of Ethernet ports, then
"connected to device" is not enough detail.)  How are they configured?

> [...] they're dropping the connection!

   What does that mean?  _Which_ "the connection"?  A wired/wireless
connection to the R7000, or a connection to the Internet, or what?  As
usual, showing actual actions (commands) with their actual results
(error messages, LED indicators, ...) can be more helpful than vague
descriptions or interpretations.

> [...] Netgear suggested I connect all three in a bridge mode... [...]

   That makes no sense to me.  Do you mean "bridge mode" as the term is
used in the R7000 User Manual, or wireless access point mode, or what?

   Visit http://netgear.com/support , put in your model number, and look
for Documentation.  Get the User Manual.  Read.  Look for "bridge".

> [...] Doing so did absolutely nothing. [...]

   What does that mean?  Did nothing different?  Did nothing?  Which
kind of "nothing"?  Did the LEDs all go dark?

> [...] the situation doesn't change no matter how many routers I use or
> which one I connect to FIOS modem.

   What, exactly, is your "FIOS modem"?  Is it a "modem", or a
modem+router, or a router, or what?

> I did master reset, [...]

   What, exactly, does "master reset" mean to you?  What does Netgear
call what you did?  (See the User Manual.)

> [...] fios replaced their modem, [...]

   With another of the same (unspecified) devices, or some different
(unspecified) device?

   Do devices which are connected directly to your (unspecified) "FIOS
modem" keep their "connection" when devices which are connected to an
R7000 lose their "connection"?

> If anyone has a solution please let me know.

   I don't yet know what the problem is.