There are at least 3 issues with UPS support in SCALE right now, I logged them with IX over the last week or so:
1) The issue selecting the driver, as described in this thread. You can work around this by toggling the Master/Slave setting, capturing all required fields for both and then choosing the Master/Slave setting you want again, afterwards. Strangely, I found this workaround more reliable if you try to start the UPS service, unconfigured, and let it fail first. Logged as NAS-109449.
2) The UPS service doesn't automatically restart when you restart SCALE. You can work around this by starting manually, or with a cron job (can't use a post-init task because these are run prior to the UPS service starting). Logged as NAS-109520.
3) The default shutdown command has a typo so the UPS service won't shut down the host. You need to correct it in UPS service configuration (should be "/sbin/shutdown -P now"). Logged as NAS-109513.