Case sent back to USCIS???

[man&dman 0]

Can someone help me? My husband entered the US on October 4th. I noticed the following notice on the USCIS website before he got here, but for some reason I didn't think too much of it at the time and booked tickets anyway.

On September 2, 2016, the Department of State sent us your case, Receipt Number, LIN**, for review. We are reviewing it, and will notify you by mail when we are done. Please follow any instructions in the notice. If you move, go to www.uscis.gov/addresschange to give us your new mailing address.

We went through the whole IR-1 process pretty quickly, about 9 months--no RFEs, simple interview, and easy POE (thank God). He received his visa on June 20th and got here October 4th. He received his social security card in the mail so we were waiting for the green card. I called today and asked why it was taking so long and they told me that they are reviewing the case and if I didn't hear anything by March 2017 to call back. She told me she didn't have any other information for me. We have been married for more than 3 years if that makes any difference. What does this mean?? They can send him back? What can we do in the meantime? Can he travel? I'm so worried that all of our hard work will be ruined. Someone please point me in the right direction as I feel lost...

[Penguin_ie 5,993]

They would not have let him in the country if there was a problem.

Physical greencards can take up to three months, and there are the major holidays in there too where USCIS shuts down; the stamp he got in his passport when he arrived acts as a temporary greencard for a year, so he can travel with that.