There is a bug when running the updater from 3.6.2 to 3.6.3. When phplist 3.6.3 is downloaded to tmp_uploaded_update, it is downloaded to directory phplist-3.6.3. The trouble is the updater expects the the directory to be tmp_uploaded_update/phplist NOT tmp_uploaded_update/phplist-3.6.3.
Resolution: The updater says “Downgrade is not supported” until tmp_uploaded_update/phplist-3.6.3 is renamed to tmp_uploaded_update/phplist
(I couldn’t figure out how to create an account on Manits)