When the Gree air conditioner displays E7, it is a mode conflict. Mode conflicts generally occur on multi-connections, which means that some rooms of your air conditioner are using the cooling mode, and some rooms are using the heating mode. So there will be a conflict!

If your air conditioner is newly installed, this will happen if the wiring is wrong. If it is an old air conditioner, I suggest you check to see if the mode is wrong?