Once you see that your prospect's email has bounced in your sequence, you have the ability to update their contact information and retry email delivery. However, depending on your sequence's ruleset's safety settings, you might not be able to add the prospect back into the sequence because "this prospect has already been targeted."
To fix this, you should go to your sequence, and find the prospects that have bounced. Click into the prospect profile, update their email, and retry the prospect. The prospect will receive the email associated with the step that bounced. View more here.