The reading with the speaker disconnected, right at the speaker terminals, should be something between like 8 to 16 ohms. They don't always give a reading like their stamped. If you got nothing, try the battery. If that does nothing, the speaker failed open, & it needs to be replaced.
Any battery like a 9 volt, C, D, AA, or AAA for examples. I usually use an AA battery. Don't connect it, just tap it quickly to produce a click.