The solution is quite simple and all you need to do is redeploy the Zimlet, using the new version, which should be on the next path

#/opt/zimbra/zimlets/com_zextras_chat_open.zip

so Switch to zimbra user and follow the procedure

#zmzimletctl deploy /opt/zimbra/zimlets/com_zextras_chat_open.zip

Then update the zimlet cache to be on the safe side:

#zmprov fc all

And finally restart the Mailbox service:

#zmmailboxdctl restart