Won't go into high 4x4

[Lance9090]

My 2000 Ranger used to always shift into High 4x4 when needed then I had to stop pull off the side of the road . Now it won't go into High 4 x4 at all. I have to physically go into low and then from low it'll go into high. I replace the motor about 5 years ago was wondering if it could be something else