3 months after FUT, nothing is visible at center. Is there something wrong?

You really can't expect to see full results 3 months after surgery.  You may see nothing.  It can take as long as one year.  If you believe something is wrong, it is always a good idea to follow up with your doctor.

Following transfer of hair, or a hair transplant, the hair will typically fall out initially.  Regrowth occurs between 2-6 months on average. In rare circumstances it may take longer. 

If you are concerned about any aspect of your surgery be sure to make an appointment with your surgeon Hairs start growing in at 2-5 months after the procedure. There are a variety of reasons why your hair might not be growing in that area.  Be sure to check with your surgeon to determine if it's normal. 

You will not see any growth for a total of 5-6 months, then it will start to grow and by the 8th month you should have 80% of it grown in by then

the hair goes through its own intrinsic growth cycle. The transplanted hair usually starts to grow in after three months and will continue to grow for up to 18 months after the procedure.

Don't worry. Hair goes into a resting phase after surgery. This resting phase can last up to four months. The minoxidil you are using is helping. Give it one more month before judging.