With that amount of information the best I can say is take it apart again in such a way that you can still turn it on and attempt to play a DVD.

CAUTION: While it is open there may be exposed 120VAC power so take great care in doing this, remember the one hand rule, of you are tapping or touching things make sure you are not grounded and only one one hand at a time touching the unit, inside or out.

If you are able to get the case off and run things, then you might be able to see what is going on, if the DVD is actually spinning or is the changer just sort of taking a small step and stopping, could be a stuck changer.

If wax got in to it that could be between gears, or other moving parts preventing some operation from taking place.

Since I take you are not an electronic's tech you will have to just use observation to see what is happening and take it from there. For example if the disc is spinning but the head is not extending look close around the head actuator/gears/servo and see if something came unseated or is stuck from the last time you took it apart or from the original damage.

Don't be afraid at some point, if you do not plan on taking it somewhere to get it repaired to tap a few things, generally you want to use the plastic hand of a small screw driver to mayby tap thing, don't let the metal part of the screw driver come in to contact with anything and tap lightly.

Agian look hard, get a good flashlight and just sit and look at various things that look like they should be doing stuff.

Again only if you don't plan on getting it fixed by as pro, say the changer is not moving, you might try to move it yourself so it aligns a DVD in the right spot and then see if the DVD spins and the head moves (to see the head move you might want to FF or hit the next section button so it should move a good amount.

Finally, you may have to disasseble it further to find the issue, like if you can't see "the works" of the changer you might need to take it apart more so you can see it.

Anyway, look for the obvious first, broken gears, belts that have slipped off or broken, springs only connected at one end or no ends, and you can always give it a shake out with the cover off, unplug it, hold it over a white sheet or something and shake it good at various angles and see if anything falls out. If something does fall out try tpo determine if it looks like it should have been there or was in there as a result of what ever happened to it.

This is all last resort sort of stuff, since the unit is broken anyway so what do you have to lose, it worse you can do is break it a little more...