Uptime plugin in server 2.8.1 does not work

Hy, i have debian 10 - Ocsinventory 2.8.1 Server -- agent 2.8.0RC
i copied the uptime.zip to

/usr/share/ocsinventory-reports/ocsreports/extensions

unziped it via unzip -a uptime.zip

and afterwards i used the webgui to install the extension

everything seems fine on server

I installed uptime plugin for windows into client into C:\Program Files (x86)\OCS Inventory Agent\Plugins

X86 because i upgraded an old client

I see no uptime on server .. regardless how often i resend inventory

i changed debug mode to 2 on client

AGENT => Running OCS Inventory Agent Version 2.8.0.1
AGENT => Using OCS Inventory FrameWork Version 2.8.0.1
AGENT => Loading plug-in(s)
    DLL PLUGIN => Searching for Plug-in DLL(s) in folder <C:\Program Files (x86)\OCS Inventory Agent\plugins>
    DLL PLUGIN => 0 DLL Plug-in(s) successfully loaded on 0 DLL(s) found
AGENT => Using network connection with Communication Server
    COM PROVIDER => Loading Communication Provider <C:\Program Files (x86)\OCS Inventory Agent\ComHTTP.dll>
AGENT => Using Communication Provider <OCS Inventory cURL Communication Provider> Version <2.8.0.1>
AGENT => Sending Prolog

....

COM SERVER => HTTP Post response received <HTTP Status Code #200>
    COM SERVER => Cleaning cURL library

is a certitficate mandatory for plugins  ?

Kind regards