Issue

After updating Photoshop your plug-ins are no longer available in the Filters menu.

Solution

Likely you just need to download and reinstall the product you own, but it could also be related to Apple silicon support.

Reinstall Plug-in

1. Download the installer for the version you own.
   Current products
   Prior versions
2. Quit out of all Photoshop applications before running the installer.
3. The host selection step should detect all compatible host programs. Make sure yours is checked and complete the installation. If the Host Selection step does not show the new Photoshop version, you’ll need to do a custom installation covered below.
4. Once done the plug-in should be available in Photoshop under Filters.

Custom Installation

1. Run the installer for your plug-in.
2. At the License Agreement screen, push Alt-C (Windows) or Option-C (Mac) and choose Next.
3. The next page will have a Custom Install button. Click it.
   
4. Select Browse and navigate to the appropriate path.
   Windows: C:\Program Files\Common Files\Adobe\Plug-Ins\CC
   Mac: Macintosh HD/Library/Application Support/Adobe/Plug-Ins/CC
   
5. Set the path to the shared location, and press Continue to complete the installation.
6. Once done the plug-in should be available in Photoshop under Filters.
   

Apple M1 Computers

Photoshop 2021 adds direct support for Apple M1 silicon but not all plug-ins support it. Setting Photoshop to run using Rosetta will allow unsupported plug-ins to run. Rosetta enables a Mac with Apple silicon to use apps built for a Mac with an Intel processor.

1. Open Finder and navigate to Applications.
2. Right-click the Photoshop application and choose Get Info.
3. Check the Open Using Rosetta box.
4. Restart Photoshop.

 

More information from Adobe: Photoshop Plug-ins Troubleshooting