I solved problem. But it also weird. When studio is open it returns "Service Unavailable" in browser, but when close studio it works OK.

My, isc.REST code at below. UnkownUser is enabled. I just  download Evaluation edition. Not,  production edition. So, just trial. Is it obstacle for it?

Include isc.REST
/// Class for REST-like web api.<br>
/// Logic related to request processing goes here.
Class isc.REST Extends isc.AbstractREST
{
XData UrlMap
{
<Routes>
   <!-- Test method-->
   <Route Url="/test" Method="GET" Call="Test"/>
   <Route Url="/logout" Method="GET" Call="Logout"/>
 </Routes>
}
/// End session
ClassMethod Logout() As %Status
{
#dim %session As %CSP.Session
set st = %session.Logout(1)
set %session.EndSession = 1
return st
}
/// Test method, outputs <b>%request</b>, <b>%response</b> and <b>%session</b> objects.
ClassMethod Test() As %Status
{
    write "{""Status"": ""OK""}"
    return $$$OK
}
}
 

But, I had compiled source from studio :)  Interesting.

Thank you so much.