Network Unreliable With New Equipment

[AudenKaitus]

So, with winter coming in we had a pipe bust and our old router is fried. The modem seems to still work but won't talk with the new router my friend gave me.

My roommate who pays for the internet decided he'd go up and ask the company and apparently they gave him this shitty gateway, which they then told him he had to call them and they would set it up remotely. Well the damn thing works, but consoles frequently switch NAT type at random and disconnect from some service but not others. And my computer, which is the only wired device to it, gets random ping spikes, packet loss, or entire disconnection from internet in general.

I honestly don't know enough about networking to get even close to an answer on why nothing works right, but the old equipment had absolutely no problems.

Some specifics:
It's a DSL connection (terrible, I know)
it's a ZyXEL AC1600 VDSL2 Combination Gateway ( VMG3925-B10A )
The default LAN IP address in the online user manual I found times out.
The company took three days before they finally called back to set the thing up so I want to avoid having to call them if I can because that probably won't help anyways.

I've still got the modem which is a ZyXEL P-600 ( P-660R-F1 ) if it might somehow be easier to try doing something with the modem and router instead of this trash Gateway. The router is a Netgear AC-1700 or something, I believe. Way over what we need, but it's a router. *shrug*

[j1404]

Wait what this is confusing what are you trying to ask?

[Lurick]

So which router is the one you were given by the ISP? The ZyXEL AC1600 or the P-600?

[AudenKaitus]

5 hours ago, Lurick said:

So which router is the one you were given by the ISP? The ZyXEL AC1600 or the P-600?

Both. The P-600 is just a modem we used in combination with a Netgear router before that router shorted.
The AC1600 is a combination Gateway.

[AudenKaitus]

6 hours ago, j1404 said:

Wait what this is confusing what are you trying to ask?

I'm trying to ask
A) What is the best way to fix the damn gateway to avoid the issues it is causing (Random NAT changes, ping spikes, packet loss, random disconnects)
or
B) Is there a way to get the modem working with my router?