If this is the first time it's been turned on since last year?
Sometimes the motor bearing will seize from residual moisture. With the a/c OFF (preferably unplugged) try giving the front fan a spin with your hand. Sometimes this will loosen up a 'stuck' from nonuse, seizure.
If it's brand new, read the installation instructions to find any shipping braces that might need to be removed before use.
Do as Dan suggested first. If the fan motor is not stuck or tight it may be the run capacitor for the fan motor. But if the fan motor is stuck or tight and you're a handy person it would be worth replacing the fan motor yourself on such a large unit. If you have to pay someone to do the job it's not worth fixing in my opinion. I've replaced a couple of fan motors over the years and both air conditioners are now over 30 years old and still going strong! If you decide to replace the fan motor be sure the condenser coils in the back of the unit are clean. Use a garden hose and spray the condenser coils from the outside to remove any dirt and debris. Usually that's what causes the fan motor to fail. Poor air circulation do to a dirty condenser. Doing this once a year at the beginning of the cooling season will also keep your air conditioner running at top efficiency! Hope that helps!