According to the IRS' website there are 3 reasons why you may be getting a mailed check instead of direct deposit as you requested. They are as follows:
- We can only deposit refunds electronically into accounts in your own name, your spouse's name or in a joint account.
- A financial institution may reject a direct deposit.
- We can’t deposit more than three electronic refunds into a single financial account.
https://www.irs.gov/refunds/tax-season-refund-frequently-asked-questions
