Works on mine. Took a second or three before it kicked in but it did and is measuring something. Currently showing 99% which might be high but it’s doing something. 

Have you tried doing just a manual O2 reading?

I just did a manual reading to make sure it's working too, and no problems there either. Measured for about 20 seconds and measured 96%. No idea if the result is accurate or not, but regardless it definitely took a reading.

Same problem here. Updated my Epix Gen 2 (not Pro) yesterday to 13.22. Now the pulsoxymeter doesn't work anymore, neither with the health snapshot nor alone. Furthermore, also the "always on" funktion and the wrist gesture are failing. What kind of an update is this, are we beta-testers now?

Check your firmware version in the System > About menu. Does it say 13.22* with an asterisk, or just 13.22 with no asterisk?

13.22 without asterisk

After a restart, everything works fine again.

try restarting the watch and doing another health check.