And even if the fuse looks OK, if it is of unknown vintage it's a Good Idea to replace it anyway. Somehow when the bullet fuses used in our cars get old they can appear intact yet fail to allow electrons to pass. (and clean the fuse contacts while you are at it, too)
As of late, I'm having more problems with the fuse 'clips' that hold the fuse. Apparently with age and heat they bend outward. I've fixed two fairly recent situations, by bending them in before inserting the fuse, where lights weren't working, one of them being my brake lights.
Check to see if you're using the 'ceramic' type fuses and not the 'plastic' ones. The plastic ones can create shrinkage as well as contact problems. I've switched to the, IIRC, NGC type in my Eyetalian cars. FWIW.