Answer by ThomasRushton ·
Any error messages? Without any actual error messages, it's hard to know where to start.
(1) Does your application have the rights to execute the stored procedure?
(2) Is your application in the right database?
(3) Is your stored procedure in the right database on the right server?
(4) does your application have different connection settings to those in SSMS? (probably...)
(5) Is the query timing out from the application, but OK in SSMS?
(6) Is it bringing back different / incorrect results?
Try http://sommarskog.se/query-plan-mysteries.html - this has some solutions to some of the above problems.