Updated Mac to OSBig Sur, loaded recent upgrade to PS & plugins all messed up

Upon realization that I'd lost all plugins after updates, I closed PS & deleted existing plugins.  Went to point of purchase & re downloaded them.

(Nik, PortraitPro being the two most critical to my work).   Restarted computer, opened PS and the plugins were there.

    Retouched ONE image with Nik silver ... worked great .... then on the very next image, tried Nik again & plugin was missing (couldn't find the path).  PortraitPro now gone as well.

   what the #@%????

any help much appreciated.  I'm nearing my wits end.   thanks