[Plug-ins TopazLabs do not work]

Here is the solution for Mac.  First let me restate the error message so it will make it easier for others to find this answer:

 

"Cannot Proceed:  IPC Memory in use or image size is too big for the system."

 

In Affinity Photo, go to Preferences.

Choose Photoshop Plug-ins.  (I assume you already added the Topaz Plugins.  You should see them."

Near the bottom right, click the "Authorize Global" button.

You will have to restart Affinity.   (It will put a path of / that represents the root directory.)

Your Topaz plugins should work now.