Gears D3 and D4 not functioning

This problem started by the car jerking when moving from gear D1 to D2, after which the car accelerates normally. I then decided to replace the automatic transmission fluid. The jerking then stopped.

One month later, I discovered that the high speed gears D3 and D4 were no longer engaging. The lever shifts to D3 and D4 and the lamps light up accordingly but the gears do not engage. The reverse gear (R), D1 and D2 engage and work well.

What can be the cause?

Thanks,

Climax