Why one day ASUS routers refused to connect to the provider?

Question

Computer networks

2 days ago, ASUS routers and some routers with alternative DD-WRT firmware refused to work with our provider.
The connection is made via PPTP.
The Internet works if directly, or through another router (The same TP-link mine did not connect with the DD-WRT firmware, after a rollback it worked)
The routers themselves seem to be connected and get their own IP but do not work, instead of the desired ip (10.10.1.15) get something like 172.16.5.67
What could be the reason for this? and how to solve this problem at the very home of 10 routers ASUS relatives.

Answer 1

What does the provider say? Did you ask him?