If the landlord doesn't accept your rental application within 48 hours, your application will expire and be automatically declined.
If your application expires, here's what to do
Try contacting the landlord again to understand why they didn't accept you. It's possible they simply missed your application, or you may not match their tenant preferences. It's always possible that the landlord will have another listing that's suitable for you, so it's worth reaching out.
Continue your search by applying to other places. And remember, you can apply to multiple places without worrying about being charged twice. Once one application is accepted, all others will be automatically canceled.