post all setting not working anymore

Which module (Library or Develop) - and if in Library, are you showing Grid or Loupe view? Even when selecting your images in the Filmstrip at the bottom of screen (which is constant), the current interface shown in main window makes a difference on whether all the currently highlighted images will receive a Paste, or only the active image.

So far as Copy / Paste, have you put a checkmark against the particular kinds of processing that you want to copy from one image, and paste onto other images?

Last, incidentally, are you aware of the AutoSync setting? 

In a first step please try resetting the preferences of Lightroom Classic:   https://helpx.adobe.com/lightroom-classic/help/setting-preferences-lightroom.html

It's recommended to backup your preferences before you reset the preferences to the default settings: 

https://helpx.adobe.com/lightroom-classic/kb/preference-file-and-other-file-locations.html