We were using the standard version of Post Grid, and felt the filter functionality would benefit our site design. However, upon installing PostGrid and enabling "filter" the filter option did not appear anywhere on the page where we had installed short code.
Additionally, the pro version did not allow us to filter based on post category and post tags.
Also, the pro version of the plugin broke custom CSS I had in place (display: flex;) to keep all posts aligned top/bottom across the rows.
We un-installed the pro version after an hour of fighting with it and are happily using the standard version now.
Welcome to our forum.
Is there any chance to fix the issues you are facing? i guess something you have missed. Hope i can help you. If possible please send me your Teamviewer Id, or temporary admin access to your site, i will check the issue.