As I recall, That API call does not work. The only way to get the receipt to not print AND get turn off the signature request to work is to leave the API mode on the terminal and login to it using the proper credentials then set these options in settings before then returning to API mode.
It sound like for whatever reason your terminal may have gotten reset.
There was a thread about this that helped me when trying to turn off the signature request
via the API didn’t work.