If you approve a song and then stop responding, the original submitter can "request an update" from you (sometimes also called "escalating" or "creating a dispute," which mean the same thing). They might be impatient, or they might have a genuine concern with the share.
When an update is requested, you've got 72 hours to respond. Head to your Approved tab and either "mark as shared" or click the chat button to message the submitter. If you don't respond within 72 hours, the submission automatically refunds.
The other direction
The reverse applies too: if an artist has gone quiet on an approved submission (for example, they haven't got the song live on Spotify yet), you can initiate the same 72-hour clock against them. See the "How do I request an update from an artist?" article for the walkthrough.