Are there any requirement on how the KEYWORD's for SMS auto replies should be configured in the ACS external accounts for SMS channel.
Auto replies are working for keywords like STOP/START & SUBSCRIBE/UNSUBSCRIBE but not for OPT-IN/OPT-OUT.
is it because of the hyphen in the OPT-IN/OPT-OUT keywords?
Yes, it's related to that.
The keyword is only suppossed to contain A-Z / 0-9 at the moment