Ceiling fan with 4 separate lights; 90 ∙ angles. 3 lights work; No. 4 doesn't. Suspect I pulled a wire loose from its connection. Where should I begin. Remote controller works fine for the fan, not for the lights. Manual only.

First, probe the light socket wuitha tester to see if it is dead while the other 3 lights are working. If dead then move on to investigating connection. Kill the power at the panel, do not trust the remote to provide a safe area for you to open the canopy.