not much to go on here but it should be one of two issues: its either the way you implemented movement or your collision settings.
for movement if your using something like set location then it will ignore collision. try using another method such as a movement component or run a check for collisions via overlapping actors or traces.
fir the collision check the collision preset and object type for both actors and make sure that they block each other. also if its a mesh that you created yourself open it in the content browser and ensure that it has simple collision. so make sure it has collision double click the mesh in the content browser then near the top look for the collision button and in the drop down click simple collision. that should should the simple collision in green wire-frame.