Slide out not working

Look for one of these. Look under the trailer, following the positive battery lead. You may find more than one.

It's an auto reset circuit breaker. Your main slide could have one all of it's own. Probably 30 amp.

Some of them have a button to push for a manual reset. Some auto reset. Sometimes the auto type, will reset when you disconnect and re-connect power.

They're available at most auto parts stores.

I don't have any advice as to what is wrong, but it might help if you let everyone know what sort of slide mechanism you have. Is it electrical motor driven on cog rails; or hydraulic; or electric motor pulling cables to extend and retract?

Was it the last slide you tried to deploy? Your battery could be weak and putting the other two out may have drained it. You can hook up to your TV, start it and see if it will deploy. If it does your battery may kaput. Had it happen at the top of Raton Pass. New battery fixed it.