In the /var/snap/microceph/xxxx/conf/radosgw.conf (where xxxx is the current number) the
run dir = /var/snap/microceph/xxxx/run
path doesn't appear to be updating.
RGW wasn't starting and found the run dir pointing a directory that no longer existed. After updating to the "current" directory number was then able to systemctl status snap.microceph.rgw.service and rgw started.