you may need to check overhead wires. If I recall right my Sister had issues and they found them using the phone lines from above and getting into her place that way
Have you ever had to deal with an infestation of pine ants (not carpenter ants). They look like regular small black ants, but have a potent pine smell when squished. From what I’ve read, they like to nest in the foam insulation commonly used in open beam ceilings.
Even though we have Clark Pest Control come out and spray regularly, somehow these nasty critters found a way in. What a PITA!