This is a guide on resolving an issue that sometimes occurs with 1998 Furbys, namely the Furby being unable to power on due to the two halves of the battery compartment not making proper electrical contact.
The terminals on the side of the upper half of the battery compartment of a 1998 Furby.
The first photo on the right shows two terminals on the upper half which connect to the corresponding prongs inside of the body, shown on the second one.
The prongs on the bottom part, with two arrows showing how they can be raised with a flat screwdriver. NOTE: the arrows are longer than the actual distance that the contacts need to be moved.
The issue with poor contact can be resolved by carefully raising the prongs on the bottom part, so that the cover closes with some noticeable friction. That can be done with a pair of tweezers or a small flat screwdriver - also make sure to keep the heights of both contacts roughly symmetrical.
NOTE: the red arrows on the image are only to illustrate the direction - you don't need to move the contacts that much!
Care should be taken not to do this excessively since those parts are relatively fragile and might snap.
It's not necessary and even harmful to lift them all the way up - the alignment should be just enough so that the contacts on the top half are reliably pressed on by the bottom ones - the door should not be too hard to close.
After this procedure is performed, inserting a set of fresh batteries and closing the cover will hopefully result in your Furby springing back to life. If not, see the "Motor force-start" section on the page here.