You won't find out why by ranting and/or asking here. What happens with your refund is between you and the IRS. The IRS will not share that information with anyone but you.
Generally, when this happens you can expect to receive a letter from the IRS in about 3-4 weeks explaining it. Usually it's because they changed something on your tax return. (Such as income you forgot to report). The letter will tell you what they changed and why they changed it. It will also include specific instructions on what you are to do if you dispute those changes. Those instructions generally have a deadline too. So if you do dispute any changes the IRS made and do not respond with your dispute by the deadline specified in the letter, then there's nothing further you can do. You just lose, unfortunately.
There's also the possibility of an offset against your refund. That offset may or may not be valid too. But you can check for that by calling the Treasury Offset Program number to see. That number is 800-304-3107 Information about this program can be found at <a rel="nofollow" target="_blank" href="
https://www.irs.gov/taxtopics/tc203">https://www.irs.gov/taxtopics/tc203</a>
