It looks like the original problem must have been with the supply as thats the common thing so as no blown fuse the most likely is that it lost contact with its holder. Over the years the holders get weak and oxidised and will suddenly break contact until you move the fuse and then all is good again for a while. You can clean them, gently bend them to be tighter and even use a bit of grease.
Now as you have the supply back on you need to see if youve got 12v getting to the interior light. Remove its bulb and use a meter to test each terminal to earth - one should show 12v. If you dont have a meter make up a tester with a 12v bulb and wire, put the wire to earth and then repeat the above test to check the bulb lights. Im guessing you wont have 12v because if the bulb is good any one of the 4 switches should operate it...