Welcome to the forums,
What zimlet are you trying to install?
A common error in the admin console zimlet upload is to have stuff zipped up one level too deep on upload.
tail -f /opt/zimbra/log/mailbox.log at the time your trying to deploy.
Have you tried
CLI zmzimletctl - Zimbra :: Wiki?
For instance:
Code:
su - zimbra
cd /opt/zimbra/zimlets-extra
zmzimletctl deploy com_zimbra_collector.zip
Shows up in the zimlets area, you drag a mail item to it and it helps add email addresses to your address book. (In the gallery
here.)
This will only apply to the default COS, so apply it to any others as you need.