1. Which Arduino is your Slave device? UNO or NANO or MEGA?
2. Show connection diagram that you have made between NANO and UNO/NANO/MRGA. Check that your connection is something similar to Fig-1 below.
Figure-1:
IDE ----> Tools ----> Board: -----> Arduino AVR Boards ------> Arduino Nano
IDE ----> Tools -----> Processor : "ATmega328P" ----> ATmmega328P (Old Bootloader)