Why does priority pass holder by AE not accepted by Alaskan Lounge

Usually it's a matter of controlling the number of people in the lounge. If the lounge is getting crowded, they give priority to the first/business class people flying with the airline vs those that access the lounge using priority pass etc

Alaska airlines lounge used to accept priority pass but that was nearly two years ago and they have not since then.

Priority Pass is not accepted at most Alaska lounges. Get the Priority Pass app and it will show which lounges throughout the world are available.