After the August update, I can no longer CROP. In DEVELOP the crop icon yields a grid overlay and I can use the cursor to move the margin. But releasing the cursor yelds NO PHOTO SECLECTED and the image is deleted from the catalog!!

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It sounds like you’ve enabled the Unedited Photos Only filter:

As soon as you make any edit, including a crop, the photo is no longer unedited and LR hides it from view (it’s not removed from the catalog).

Toggle that button or do the menu command Library > Enable Filters to disable filtering.  (See the menu command for its keyboard shortcut.)