If the pops do work but are slow to react it's just a matter of switch adjustment and cleaning of the spoon. The skirt assembly under the playfield comes down to a small extension that sits in a dish or bowl looking leaf switch. Touch the skirt on the top of the playfield with your finder to see how much action it creates on the skirt/spoon to close the contact that initiates the pop bumpers. The spoon itself is sitting upwards so it tends to get grimy and gummy, clean it off.

While your there it's a good idea to clean the contacts too. Don't make them too touchy as they can then pop due to playfield vibration in the vicinity.

Also make sure the end of stroke (EOS) contacts for the pop bumper allow for almost full travel before closing these EOS contacts, provides the intended power.