I have a teleport door in my living room that takes me to another house.

At that house I have a second teleport door that I want to link to a third house.

However, when I use that second teleport door, I get the message 'the other teleport door is not currently available'.

I get the same message when I try to use the teleport door at the third house.

What am I doing wrong?

Hope I'm understanding right, but did you place the 4th teleport at the other home?
Meaning one in a home goes to the another one. You'd need to put one more in that home, and the 4th one in another. Or maybe you have more than 1 in your inventory and the wrong one was placed? Hope that made sense.

It does make sense. I'll try it. Thanks.

no worries.
Ways to Link
1. Your Telport to your telport to another home.
2. Your telport to your telport in same home different room
3. Your telport from any home to an Avenue
4. Your telport to any other Avenue.
The message is that one of the telports is not connected.
If you have 3 telports which it sounds like they are 1 of your other ones is missing.
Where can it be?
in your inventory ... If it is in inventory no problem go set it down someplace. If it is not in your inventory then you gifted one to someone or someone gifted it to you ..
Gifting from the gift app is the only way to gift a telport door.
You cannot gift it by buying them at the store, going to your inventory and gifting it.
You can only gift them by seeing your friend and clicking to gift them from the store app on their avatar or their gift app in their home. You can shop for them and use that gift app for thes old out of date gifts no one wants.
That is how you can gift a telport door by this app.
Since it seems like you have 3 doors, someone gifted it to you and did not put thier half down or they delteted it and now yours is useless. Or they stopped playing and did not tell you.
Hope that helps.
I hate tellport doors.
I have over 100 useless grey doors on one avenue. Bvg ruins a lot of plans by not telling me how things work.