to be a valid JSON, it should be instead :

Here is a quote from MCP23017 specs :

The INTn interrupt output can be configured as active-
low, active-high or open-drain via the IOCON register.

The ESP8266 forum is not dead : https://www.esp8266.com/index.php

Your while loop doesn't check buttonState anymore after entering the loop ...
You should do that instead :

Do you have some MOSFETs or any kind of drivers, such as ULN2803, between MCP23017 and the relays ?
Because MCP23017 output can't provide enough current (max 25mA) to drive relay's coils directly ...

ULN2003 isn't the best for that purpose, especially that saturation requires input level greater than 2.7V.
You're better using MOSFET with low Vgs, such AO3401, where saturation could be achieve with only 1.3V.

rtc_get_reset_reason() from "rom/rtc.h"

https://github.com/espressif/arduino-es ... .h#L82-L99

Do you placed a PullUp on RES pin of the TCA6424 ?

What do you think ?

You need another delay after bringing back the lines to HIGH ...

The display shows "c : 0" continuously.

You need to have your declaration "uint32_t c = 0;" to be volatile, ie "volatile uint32_t c = 0;"