This is a pretty common issue and here are some possible causes
- Most commonly If you have a low amount of transmission fluid in your vehicle, you could have problems reversing your vehicle. Low transmission fluid can cause all kinds of problems with the gears, such as gear slippage, shifting problems, and overheated gears.
- One common problem that can happen with a clogged filter is difficulty moving in reverse. The lack of fluid flowing through the transmission can cause the reverse gear to lock. This may prevent the vehicle from going in reverse altogether, or it may cause it to hesitate before launching into reverse.
- Every automatic transmission has a valve body. This is large, maze-like component that directs the flow of hydraulic fluid to the valves. This is what allows a car to smoothly shift gears whenever the situation calls for it. In case of a bad transmission valve body, you may experience delayed shifting into reverse or simply nothing happening after shifting in reverse and stepping on the gas.
Sometimes the transmission fluid gets contaminated with enough hardened deposits or other gunk that it actually affects a vehicle shifting into reverse or other gears. While not that common of an issue, changing the transmission fluid and filter (if your car has one) is a cheap course of action.