Queries on model doesn't work

[MehdiAghighi]

i am using this package for comments but when i use the model to make a query with a where method on a column it gives no result !

for example

Comment::where("user_id", 2)->first()

returns null Nested Set Collection instance but i am sure i have a comment for this user in the database. also when i use

DB::table("comments")->where("user_id", 2)->first();

it works and gives me the record. but the model can't fetch the record.

UPDATE : also i checked any other where conditions doesn't work . even ->where("id", 1) doesn't work for example !