Hi @didier-walraet ,
are there any errors in Nginx or PHP fpm logs?
Could you also post the request and response json when you open mobile devices in web? The easiest way to do this is to open the Developer Tools and Network tab in them. The request looks something like this: {"zarafa":{"pluginmdmmodule":{"pluginmdmmodule1342":{"list":{"restriction":{},"groupDir":"ASC"}}}}}
.
Just be aware that the response contains the device id, so you might want to alter it before posting here.