on android,  whenever i am sending a  GS MatchmakingRequest , it always sending this : 

{
"@class": ".MatchmakingRequest",
 "matchGroup": "group1",
 "matchShortCode": "MULTI_MCH",
 "requestId": "1497112646_6"
 }

 
but from windows  same  GS MatchmakingRequest  sends  this:

{
    "@class":   ".MatchmakingRequest",
    "matchGroup":   "group1",
    "matchShortCode":   "MULTI_MCH",
    "skill":    18,
    "requestId":    "1497116723_49"
}

 
so in Android it always missing:

 "skill": 18,

as a reuslt the rsponse always this in android:

UGameSparksModuleLog: WebSocket callback: {"@class":".MatchmakingResponse","error":{"skill|action":"Must provide one of skill|action"},"requestId":"1497112646_6"}


is this an android specific bug ?

i have stopped working on that because of these issues with ue4 plugin of gamesaprk. 
 ue 4.15 and 4.16's gamesaprk plugin is totally broken. 
so cannot answer you for now .
  i Will inform you if i again continue to work on Gmaespark for Android.