Hi emilu,
connect? What does it mean?
You can create apps in the existing environment directly.
Sign in to Power Apps, Choose the environment you need by selecting the environment icon 
--Deleted environments do not appear here.

Select Solutions from the left navigation pane, Open or create a new one solution.
--Select New > App, then select you want app type to create.

For your question: my sandbox app was deleted and it's past the time when I would be able to recover it.
Generally, you can recover a recently deleted environment (within 7 days of deletion).
If deleted for more than seven days, you need create a support ticket for Microsoft Support team and if they can find this environment in the backend database they can restore it.
Get Help + Support - Dynamics | Microsoft Docs
If it can't be restored in the background, then you have to go and create a new sandbox environment.