When we try to install the zimlet with the command: install.sh zimlet, the following message was presented:

Deploying zimlet ...

com.zimbra.cs.account.AccountServiceException: no such zimlet: com_zextras_zextras
at com.zimbra.cs.account.AccountServiceException.NO_S UCH_ZIMLET(AccountServiceException.java:274)
at com.zimbra.cs.zimlet.ZimletUtil.setPriority(Zimlet Util.java:1150)
at com.zimbra.cs.zimlet.ZimletUtil.dispatch(ZimletUti l.java:1939)
at com.zimbra.cs.zimlet.ZimletUtil.main(ZimletUtil.ja va:2010)

Zimlet installation failed. Exiting.
The Zimlet installation has failed. That might be due to an incomplete startup
of the Zimbra webapp. Please verify Zimbra is up and running, then retry
the deployment of the zimlet with ./install.sh zimlet .

Following information:

Ubuntu Version:
Ubuntu 16.04.1 LTS

Kernel Version:
Linux zimbra 4.4.0-24-generic #43-Ubuntu SMP Wed Jun 8 19:27:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

Zimbra Version: 8.8.12_GA_3807.FOSS

Zextras version: 2.16.1

What procedures should I perform?