Feeling fairly stupid now...

I have Comcast Digital phone service/modem (xfinity) connected to my old phone setup. Was working fine until recently callers could not hear me - I could hear them fine. Started to troubleshoot looking for bad connections, shorts, etc... I learned that I could just plug in to modem line out which works fine for one phone. I got a splitter to plug into modem allowing me to add a second phone on same line, but I can't seem to get the second phone to work. I've rewired the second phone from wall jack to modem and still won't work. I tried connecting the phone on a short cable close to the modem and it worked so I'm sure there is a bad connect in that line somewhere. I had to use butt connectors to connect/extend the line and new plugs for new cable, so there must be a bad connection there but I just can't find it. Now I'm thinking of going back to my old setup / NID, but I've cleared out some of the old NID wires and it might be a challenge to replicate.
I need advice as to whether I should try to go back or if I should continue to trouble my modem connection issue.
I've noticed that the caller ID I would see on the TV is not working anymore.
I have what I think are 2 NID's connected to each other - older terminal type and a newer gray box.
Not a lot of info I know but I'm hoping for some guidance.

I can't tell what you have or how things were connected. I'm assuming you have 3 telco locations: TV, phone 1 and phone 2.

Question: Where is or was the place where all of the wires come together. The old NID?

Inside the house?

Are your cables CAT5 or better or are they the old quad wire?

I'm envisioning all of the phones going to the old NID.

Lowe's has a small punch from Leviton down block that can be used to distribute the telephone wires.

Bunch blocks (tried to find my source) are available to make multiple separate screw terminals available in the NID. This is great for troubleshooting.

Splicing telco cords can be problematic without the proper splice connectors. Scotchlok is one particular type that's used.

I probably would have done a new NID to old NID run if that's where everything was terminated.

I'd consider a new demark point inside using the punch down leviton telco block.

Thanks KISS for your answer/reply,
Yes, the NID's are in the basement and the wiring is the old quad type.
I'm totally ignorant about all of this so please bear with me.
I think I understand that the punch down will clean up / simplify things for me. You mention considering a new demark point. Could you please elaborate on how this all fits together?
I've attached photos:
32702

32703

32704

Thanks

So the grey NID is not in service and the two old protectors are gone.

The writing on the NID looks strange with a red to the top 1/2 ringer and a green to the bottom /2 ringer.

I think what might be happening is a polarity problem. Some phones are sensitive to polarity reversal and others are not.

Telephone wall cables are mirror images of each other. Ethernet cables are not.

Do you own a voltmeter?

I'd suggest swapping the two middle conductors of the telco cable or testing the polarity of the line.

Another possible lssue is in the plug termination. There are plugs made for solid/stranded cable and for stranded cable.

The stranded only version has one piercing pin. The solid/stranded has three per wire.

That isn't too bad of a setup.

An alternative:

1. Cable the modem to the protector side of the NID
2. Move the 2nd set of protector wires to the top protector.
3. Use one 1/2 ringer for one line.
4. Use the second 1/2 ringer for the second line.

The test jumper could isolate either line.

So, best guesses at this point is:
1. wrong polarity
2. A telco connector inappropriate for the wire used.

The white wire is probably solid and that's probably the line your having problems with.