There are several factors that may cause a garage door to bow in the center.
Garage door bows when opening.
Garage door struts are available at home improvement centers to fix your bowed garage door.
You might have absentmindedly unplugged the operator as you were exiting the garage through your internal door to the house.
I believe there will always be a slight bowing as the pushing and pulling of the door exerts pressure on the rail.
Doors without openers have no brace preventing warping and swelling at the top of the section.
Sometimes a garage door won t open or close for one reason only the operator has no power connection.
My only suggestion is the ensure that the door operates properly and easily without the gdo and then re connect the door.
In other cases the weight of the garage door in conjunction with an automatic garage door that is attached to the center of the door may be the cause of bowing.
In some cases basic exposure to the elements along with temperature fluctuations may result in bowing.
In the funniest of scenarios the problem will simply be due to an unplugged power cord.