Unable to activate wifi only iPad

Have an old iPad that has been working fine for years. Now it says it needs to be activated. Repeatedly I receive the message that the activation server is unavailable. So I tried connecting it to iTunes on my Mac. There I get an error message saying it is unable to obtain the activation data from the device, make sure the sim card is inserted correctly. It's a wifi only model of iPad, there is no sim card. Now what?