Stack forced mode does not become active until there is a stack in place that has broken. Once that happens, then stack forced mode will activate on the standalone switch. The standalone switch will operate in a stacking operation, where the stack IP becomes active.
If there was not a stack in place prior to an outage, where the units are both in standalone and did not have an opportunity to form a stack, then the switch will not use the stack IP and will not enter stack forced mode. This is normal operation. As a workaround, you can set up each unit with a switch IP for remote access.