Check-In showing “not available” for only one contact

I have ios 18.0.1 running on my phone and I was unable to send my check-in in iMessage to only one of my contacts. It showed as “not available”. It worked for everyone else I attempted to send to. As soon as this contact updated to 18.0.1 as well they were unable to send a check-in to me, but were able to before updating. We were able to send check-ins on ios 18 before the most recent update.

Is this a glitch with the newest update?