Hi Komal and at first a want to thank you for your help.
I've installed UVDesk by using composer.
I've executed the command you are mentioned in your Post, but this doesn't change anything with my problem.
Here are the Versions I am using regarding UVDesk:
UVDesk Community Helpdesk Automations Bundle
Generic purpose composer plugin to auto-configure your packages
UVDesk Community Helpdesk Core Framework Bundle
UVDesk Community Helpdesk Extension Framework Bundle
The Mailbox component provides tools that allows your helpdesk ...
UVDesk Community Helpdesk Customer Support Center Bundle