Flash bulbs go off with low voltage and will burn your fingers if you are holding one when it goes off.

The problem is likely corroded battery contacts, corroded/tarnished socket, tarnished/corroded switch contacts.

If you have a volt meter you can check the batteries, and socket when the red button is pressed.

There are automotive bulbs with bayonet base that will fit the Graflite socket. If everything is working, you'll see a momentary "flash" of the bulb. Works best in a darkroom!

(Off topic: I've used a 12V automotive bulb as a replacement head lamp in a Lionel locomotive, specifically the 2020 6-8-6 S-2 steam turbine. It has that same bayonet socket, too.)