What did you do when teenagers no longer want to camp?

Go Dogs--First of all--Don't let them bury their faces in the phone and computer. I believe the parent pays the bills and, therefore, controls the devices.
I was in Bryce this summer. A large 5th wheel pulled up with apparent grandparents and 1 surly boy, wearing his cap pseudo-gangster style, about 14. He didn't want to go sightseeing and wanted to stay at the 5th. They planned to be gone 5+ hours. The grandfather said OK.
I would have said OK, gotten him out of the 5th for a second and locked the door. He could spend the next 5 hours hanging around outside the 5th or the visitor center.
Zero chance of him being inside playing on the phone, sleeping, watching TV.

I think there is not much worse than dragging a teenager, anywhere that they didn't want to go. Their face buried in their phone or computer, grunts instead of words, not wanting to participate in anything. Makes for a miserable time for everyone. Hopefully, you can make it interesting for them. If you can stomach more kids, taking a friend sounds like a good idea.

Tell them, "Tough pickles, this is what we are going to do."
That's what my folks told me when I didn't want to go on a family activity.

As soon as they get a job and start supporting themselves, then they can go their own way. For now, you are paying the freight so you get to decide where the freight goes.

Get them a room at the local Ritz and go camping.

Make them stay with my mother in law. They'll beg you to come pick them up and take them with you... Just kidding (kinda).

But I agree with the poster above that you need to change your future plans a little and take them where they might really be interested. If they love sports, you might make a camping/sports venue trip, etc.

But as mentioned before, have them invite their friends. I'd much rather have them around me with their friends than at home where it's hard to keep tabs on them.

They're too young to stay home alone. Try to find something fun for them to do while camping.

Drop them off with a mean Aunt and then go camping. They'll be chopping at the bit next time......:B

Changing the style of camping MAY keep them involved.
Teenagers reach that age were doing things with the folks is considered lame....tough to overcome.

Part of that cutting the apron strings.
Let them go to friends house for the weekend?

I was fortunate that my Son enjoyed going.....wife not so much. So Son & I went camping/hunting together.....30 yrs. later we still go on trips together.

If they really liked it as a child. They may stop going some in their High School years. But they will come back, and the will bring friends. We had to go from a pup to a 10 person Bunkhouse, to accommodate the "Friends" meaning the GB, and SIL, and DIL.

We began to take them where THEY wanted to go; whether it be more rustic or more recreational. Let them bring friends and didn't go for more than a few days. OUr kids love to camp with us now in their mid 20's and never really stopped. Bought them a little pop up for their own hotel now. We would leave them at home after age 16 if they didn't want to come and have friends and family check to be sure there weren't any get togethers at the house. I admit though, we were very lucky to have them come 90% of the time.