ESP8266-01S Stopped responding after second launch
You need to re-flash your AI Thinker firmware. AT+IPR kills certain versions of the firmware.

Install the latest version of the firmware and use AT+UART_DEF=9600,8,1,0,0 and AT+UART=9600,8,1,0,0. (The former sets the default baud rate, the latter the current baud rate).

You can read more here.