routerlogin.net not working after disabling DHCP

> [...] Care to explain a little more?

   What you want is to configure the RAX75 as a WAP.  A part of that
task is to disable its DHCP server, but that's only a part of it, not
the whole job.

> [...] I thought I made it clear that a Factory Reset is not what I'm
> looking for. [...]

   Yes, but I skipped right past that, assuming that with no DHCP server
running on the RAX75, little else would be working among the devices
connected to it, so that a settings reset would be relatively painless.
Which would be even more likely after any existing DHCP leases expired,
and could not be renewed.  (Also, if you didn't know what a poor idea
disabling the DHCP server was, then I wouldn't bet that you hadn't
committed some other configuration blunder(s), so that a settings reset
would be a good idea, generally.)

   But, fine.

> So, I just disabled DHCP on the Netgear and let the ISP router take
> care of assigning IP addresses for all the PCs.

   I would not expect the (unspecified) "ISP router" to be able to do
that.  DHCP uses broadcast messages, and those generally don't get from
the LAN side of a router to its WAN/Internet side (where the remaining
DHCP server resides).

   A possible exception would be if the connection between the
(unspecified) "ISP router" to the RAX75 was made using a _LAN_ port on
the RAX75.  And that seemed unlikely if client devices connected to the
RAX75 had been getting addresses on a different subnet ("192.168.1.*").

> [...] 192.168.1.1 will not work since DHCP is turned off. [...]

   Disabling the DHCP server, by itself, would not shift the RAX75 LAN
IP address from its default of "192.168.1.1".  What I _would_ expect to
happen would be that a DHCP-using computer which was connected to it
would not get valid IP parameters (because there's no local DHCP
server).

   "will not work" 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.

> [...] I've found the IP address for the router, [...]

   How?  What, exactly, did you find?  If you found this (mystery)
address on the (unspecified) "ISP router", and it's on the "192.168.0.*"
subnet, then I'd guess that that's the address of the WAN/Internet
interface of the RAX75.  Normally, that wouldn't work because the RAX75
would see an attempt to connect to its WAN/Internet port as "remote",
and "Remote Management" is disabled by default.

> [...] If I try routerlogin.net, I get redirected [...]

   "try" from where?  There are multiple reasons for a computer to get
to that misleading/useless error page, generally involving use of a DNS
server other than the relevant Netgear router.  See, for example:

      https://community.netgear.com/t5/x/x/m-p/1976674

   If the RAX75 WAN/Internet port is connected to the (unspecified) "ISP
router" LAN, then I'd expect its LAN interface still to be at
"192.168.1.1".  And, if you connected a computer to it (probably by
Ethernet), and configured that computer's network interface manually,
using parameters like:

      Address: 192.168.1.x   (x = something big, perhaps 200?)
      Subnet mask: 255.255.255.0
      Gateway: 192.168.1.1

then, I'd expect a web browser on that computer to be able to reach the
RAX75 management web site at "192.168.1.1".  And you could re-eenable
its DHCP server.  And/or configure the RAX75 as a WAP.  Which I'd expect
to disrupt the RAX75 LAN client devices about as much as a settings
reset on the RAX75 would have done, because they'll all need to get new
IP configurations on the "192.168.0.*" subnet.

   Hence, I'd suggest a settings reset, and then configuring the RAX75
as a WAP.  But, "If a man wants to carry the cat home by the tail, I say
let him.  That cat will teach him a thousand lessons which I could never
explain."