Keep Coding

we have this 2 eloquent script which retrieves a user video based on the filter. I know this is working before because I haven't received any complains from the testers and my superiors have verified it is working.
$previous_winners = Stage::whereNotNull('win_date')
->where('win_date','>',Carbon::now()->subDays(8)->format('Y-m-d H:i:s'))
->lists('userId')
->toArray();
output for the 1st script is like:
array:4 [
0 => 84
1 => 361
2 => 304
3 => 326
]
but the output of the script below is null
$stage = Stage::whereIn('stageId',$id)
->whereNull('win_date')
->whereNotIn('userId',$previous_winners)
->where('stageId','!=',Config::get('constants.intro'))
->where('stageId','!=',88)
->first();
When the controller is called I always get a null value for the 2nd script even though when I checked the data it should retrieve one as I forced it to return results. The issue that I found out is that when removing this line ->whereNotIn('userId',$previous_winners) i get the correct results but when I put it back again i only get null values. I tried moving the whereNotIn to different positions from the first and before the end but as long as it is present I only get null values. Any idea or workaround on this one, please? Thanks.