run this command
[zimbra@mail ~]$ zmzimletctl listZimlets
Installed Zimlet files on this host:
com_zimbra_date
com_zimbra_email
com_zimbra_phone
com_zimbra_url
Installed Zimlets in LDAP:
com_zimbra_amzn
com_zimbra_date
com_zimbra_email
com_zimbra_phone
com_zimbra_tracking
com_zimbra_url
com_zimbra_wikipedia
com_zimbra_xslt
com_zimbra_ymaps
Available Zimlets in COS:
default:
com_zimbra_date
com_zimbra_email
com_zimbra_phone
com_zimbra_url

but nothing shows in web UI, even after refresh.

Thanks!