I had the same "currently unavailable" problem. Called USAA technical service, and they were absolutely clueless. Said they had never had such a problem. Tried the chat function here, got a Page Currently Unavailable message. Looks like USAA has forgotten what it means to serve.
Thank you for reaching out in Community. If you are still experiencing the problem with Deposit@Mobile, please contact technical support at 877-632-3002. They should be able to provide assistance and if necessary open a trouble ticket for the issue.