Posting here for the benefit of anyone else having this issue. What I ended up doing was contact smartthings support chat (https://support.smartthings.com/hc/en-us) and they checked my hub v1. Apparently it’s Zigbee firmware was out of date, which apparently the hub firmware and the Zigbee firmware on the hub are separate, and there’s no way for the user to check the Zigbee firmware. Support however was able to push a Zigbee firmware update to my hub, and then pairing worked just fine, as documented here: https://support.smartthings.com/hc/en-us/articles/213496343-Samsung-SmartThings-Multipurpose-Sensor
You’re welcome.