Here are some possible reasons:
1. The Aged Receivables report shows Unapplied Credits (because these are part of your A/R balance). These do not display on a Delinquency report.
2. The Aged Receivables report will show anyone with unapplied prepayments, even if their balance is zero. You might need to manually apply those credits with Apply Available Balance.
3. Future dated transactions can cause the two reports to be different. Check the resident ledger for any future transactions. Don't forget to look for Hidden transactions as well.
Permissions and Settings
To run aged receivables and delinquency reports you need permission. To check permissions, go to Admin > User > (Select User) > Change Permissions > Reports > Transactions.