In https://build.opensuse.org/package/show/home:firstyear:kanidm/kanidm which
has the config for services:

  <service mode="disabled" name="obs_scm">
    <param name="url">https://github.com/kanidm/kanidm.git</param>
    <param name="versionformat">@PARENT_TAG@~git@TAG_OFFSET@.%h</param>
    <param name="scm">git</param>
    <!-- <param name="revision">master</param> -->
    <param name="revision">v1.1.0-alpha</param>
    <param name="match-tag">v*</param>
    <param name="versionrewrite-pattern">v(\d+\.\d+\.\d+)-alpha</param>
    <param name="versionrewrite-replacement">\1~alpha</param>
    <param name="changesgenerate">enable</param>
    <param name="changesauthor">wbrown@suse.de</param>
  </service>

Despite changes generate being enable, changes are never generated or added to
the kanidm.changes file. I have been able to reproduce this on other projects
too. 

No errors are raised or warnings reported. It silently fails.

obs-service-obs_scm-common-0.10.16.1595245235.15a0df2-1.1.noarch
obs-service-obs_scm-0.10.16.1595245235.15a0df2-1.1.noarch
osc-0.170.0-2.1.noarch