Welcome to the Community,
>>> ... I've recently deployed vCSA 5.5 and than vSphere web client ...
where did you install the Web Client, and why? The vCenter Server Appliance (vCSA) already has the Web Client (which is actually the server part) built-in, and there's no need to install anything - except for the plugins - on the machine you use to access the vCSA via a web browser.
André