frank1492 top-poasted:

Thank you all for your comments. It is clear that the interface
box doesn't require disconnect of the phones to tell if it's a
TELCO issue

That tells us exactly nothing about how your premesis wiring is
connected to the demark jack.

but I did disconnect the phones and the DSL modem and there is
nothing.

You don't post here that often, but I hope you do come back and tell us
what the problem was.