This will work fine. it is related to syntax error. Use proper syntax to write query
public string getSubs(string username)
{
var query = from s in db.Subscriptions
join u in db.UserDetails on s.sUID equals u.uID
where s.sPriceABS_ExpiryDate >= DateTime.Now &&
s.sPID == "163"
select new
{
u.uID,
u.uUsername,
u.uPassword,
s.sPriceABS_ExpiryDate
};
}