If you have the 2.0 engine, it has the dual clutch transmission. You might need a new clutch pack, but first removing and cleaning the engine/transmission ground connections to the body. They are under the air filter box. Clean the body underneath the bolt heads to bare metal, and reassemble with a dab of grease. Doing this will also reset the TCM, so drive it moderately the first time you drive it afterwards. Here is a rather long video tutorial; skip to the good parts...
If that doesn't work, you can check the clutch forks for binding by removing the actuators (they use E-Torx sockets; I picked a up little set at Harbor Freight) and seeing if the clutch forks move freely using the clutch reset tool (available on Amazon and elsewhere.) It should turn counterclockwise in smoothly about 14 turns and return by itself smoothly. If it binds, shoot in some brake cleaner and carefully work it in and out to see if you can free it up. once it's free, give it a shot of silicone spray and work it somemore. Here is a short video that talks about the forks...
If those don't help, you likely need a new clutch pack.
The EcoBoost engine uses a conventional torque converter automatic, so if that's what you have, ignore the above advice.
