After you file

I filed my taxes 1/28 and still have not received  them or a letter! I was told I was under review but they don’t know why and told me if I haven’t reviewed my return or a letter by 4/15 to call back!!!! I started off with code 1541 and went to processing with it has said that now for over a month. Nothing on my return was different then any other year so I’m just confused