Not enough information.

Could be the derailleur cable was installed too loose, or with the shifter in the wrong gear/position when the cable was pulled tight. What gear did you have the shifter in when you installed and tensioned the front derailleur cable?

Or, the front derailleur and/or the shifter could be defective.

Or, the front derailleur could be the wrong type/pull. Some front derailleurs are designed to pull the cable up and are used for top ruted cables. Other front derailleurs are designed for pull down, and are used with cables that are routed down by the bottom bracket. Other front derailleurs can be used for top pull or bottom pull, but you must route the cable correct for it to work.