The listing expires, it comes off the MLS® system, and you are free again. The important part is what you do before that date, not after it.
Your listing agreement runs for a fixed term. If nothing sells before it ends, the listing expires, comes off the MLS® system, and you are free — relist with the same REALTOR®, list with a different one, or do nothing.
One thing does not reset: the listing history stays visible to agents, so a buyer’s REALTOR® can see the home was on before, at what price and for how long. Ending a listing early, before the term is up, is a separate question — how cancelling works in Alberta →
There are only three reasons a home does not sell, and they need different answers.
An expired listing that returns at the same price with the same photographs is the most common mistake here, and buyer agents notice immediately.
See also: what it means when a home comes back on.