I have a question about my landline phone. What could be wrong here?

My landline phone no longer has a dialtone. If I try to call the phone from my iPhone, I can hear the line ringing through my iPhone speaker. However, I can't hear the actual landline phone ringing. What does that mean? Do you think the line still works? My home office is a bit cluttered at the moment, so I can't reach the wall jack. But I'm going to check later.

The wall jack is the most likely culprit. Otherwise the line or the phone could be broken. The way to test is to plug in a phone you know to be working. If that doesn't work, the line is dead.

Loose connection or broken wire.

If your phone is portable, it has a battery which may need to be replaced.

Jack as some have said, could have simply become unplugged.

Simply way to figure out how to troubleshoot for yourself.

Check to see the phones plugged in if it's handset or portable phone try replacing the battery. If you have another phone that works try plugged into the jack. If none of that works it's probly the line. Call your phone provider to troubleshoot further. They will also be able to send a tech out if needed.

If your landline were working then if you call it from your iPhone and pick up the landline handset you should get a connection - if it doesn't then for whatever reason it ain't working no more!

Regards the "ringtone". The ringtone that you hear on modern systems is produced by the telephone exchange, to let you know that the circuit is in place. Once the circuit is in place it will make a ringtone whether or not there's a phone connected!

Your line card in the local exchange sends both dialtone and ringing current to your phone.
In between are the external line, a master socket, possibly a microfilter, and a phone cord.
( If you are using a cordless DECT phone then it will give you those symptoms if the mains power is off or the batteries are flat, so check those ).
Otherwise there's a disconnection in the wiring between your phone and the exchange as the exchange will still ring to a disconnection and it will prevent you calling the exchange by looping the pair of wires to get dialtone.
Watch this BT video to save yourself a call out fee as the service provider is responsible up to and including the master socket, after that you are;

BT can easily remotely test your line and find where the fault is before sending an engineer by the way, so it might be worth asking them to do that for you. This applies to other companies also.
Regards, ex BT Bob UK.

A lot of different things could be wrong (one at a time, of course).

The only way to know exactly what is wrong
is by performing a systematic examination of the phone
and the line to which it is connected.

If necessary, call in an expert to help you.

The reason why you hear a ringing signal when you call your landline from another phone
is because that sound is generated separately from the ringing voltage impressed on the line.

You might be surprised to learn that they don't occur at the same time ---
the ringing voltage goes out first, then the tone you hear when you call is sent "back".
They alternate until the call is answered or terminated.

Once you get the phone working again,
call it from the same room to hear what I described.