Will not go into drive

The most likely cause is low fluid level. Any abnormal slippage will seriously accelerate the clutch plate wear. That alone can result in a failure to more. Debris breaking off the fiber plates can also tear up the rubber lip seals in the clutch packs. Reverse is usually the last gear to go because the line pressure is much higher in reverse, and that can be what is needed to keep the clutch from slipping.