Telescoping steering wheel not working

Hello all, new member here with a question about my recently acquired '87 560 SEL. It's a really clean, unmolested 55k mile car, but the telescoping wheel doesn't seem to work. I've tried operating it per the owners manual (door open and ignition key off, door closed and key in position I or II), as well as just about every other combination of key and door position, but it just does not work.

All other electric accessories work (power seats front/rear, power headrests, power windows, power sunroof, heated seats front/rear), except the clock. I've checked the fuses; they all look fine.

Any ideas on what I should check next?