Try changing the starter.
Starter solenoid? Battery not fully charged?
To change the ignition key core on a 1992 Toyota Previa, first disconnect the vehicle’s battery to ensure safety. Remove the steering column cover by unscrewing it, then locate the ignition switch assembly. Use a flathead screwdriver to press the release pin on the ignition lock cylinder while turning the key to the "On" position, and then pull out the old cylinder. Finally, insert the new ignition key core, ensuring it clicks into place, and reassemble the steering column cover.
Multiple "clicks" check for a weak battery Check fr loose or corroded battery cables Single "click" Maybe a bad starter solenoid
Did you check your starter?
dying battery, loose connection More Likely: I had the same problem. Solved by replacing the contacts INSIDE the starter motor. You can buy the contacts online or from Toyota dealer. It can be a DIY if you are a little handy.
Possibly the battery has run down. Process of elimination, check to make certain battery cables make good contact with the battery, charge the battery, have it tested, or receive a boost. Next if unsuccessful check the starter, and alternator.
Bad battery, starting motor or both.
Dead battery or a bad connection to the battery.
two very good possibilities are the battery, and the starter. its easy to test, just try to jump start it. if it still just clicks it needs a starter. if it starts its probably the battery.
Low battery voltage will cause clicks, and it is also possible that the starter solenoid is too worn in which case replacing the whole starter is best.
Clicking can mean a loose connection between battery and starter. Follow wire to starter and clean/tighten connector at starter.
If the battery is bad, you may only hear clicks. It could be the starter, but I would check the charge on the battery first.