As of June 24th, 2021, the State of Washington will no longer honor concealed carry permits from Oklahoma.
I was unable to find the reason for the change. However, changes are quite often due to the requirements in one state not meeting the desired requirements of another.
As you can see, even state websites are sometimes not accurate. However, we try to keep you abreast of changes in gun laws that affect you. The best resource is our book Legal Boundaries by State. It is available as a hard copy and digital copy. It covers reciprocity, state gun laws, and federal laws pertaining to traveling with firearms across state lines. The digital copy is regularly updated, and you have access to the digital copy when you purchase the hard copy version.