While your Memberium version should always be one of the first things to check if you start experiencing sudden or otherwise "unexplainable" membership behavior. This fix is specifically regarding upgrading to >2.191 if you start experiencing issues after many WordPress instances automatically upgraded to the Nov. 10, 2021 security patch (5.8.2|5.7.4|5.6.6|etc.). We resolved issues for several of our own and client sites by upgrading all Memberium installations specifically past version 2.191.