'88 80 brake light alarm?

["Larry P. Rudiger" <lrudiger@zoo.uvm.edu>]

Hi, crowd. New to the list and new to a rode hard/put up wet 1988 80
Quattro.

I've replaced all four tail lights (I think there are but 4, and this
assumption could be the start of my problem) but the dashboard computer
alarm still tells me that something's amiss: it alternates between "break
light" and a little icon of a bulb with a circle/slash, suggesting a bad
bulb. Also replaced all ten of the Libby Lights--those little ones at the
top of the rear window. Snugged up connections into the rear contacts. Fuses
seem okay (can anybody tell I'm grasping far beyond my automotive
knowledge?) and out of ideas.

Any help much appreciated.
Larry Rudiger