Hi Guys - I followed the advice to upgrade to V4 (including the warnings this would remove the older version) and it seems to have worked for DXO 4 elite, but I can’t manage to get it right for Affinity photo.
Take a look at the on-line user guide for Nik Collection at Installation, activation, and uninstallation and you will find the install instructions for using with Affinity Photo. I am running macOS Mojave but had a problem because I followed the instructions for setting up as was done in Nik Version 2.5 and 3.0. It is a bit different under Version 4. If however you have followed the instructions for Version 4 from the user guide then you probably would need to contact customer support. I have always found the customer support at DxO to be very helpful and responsive. Hope this helps.
MacOS or Windows; which version?
If Mac, did you purchase from MAS (Mac App Store) or directly from Serif? I have noticed differences for specific plugins, but both versions should be able to run Nik4.
Nik Collection is now working as designed on my iMac (Catalina), using Affinity Photo Serif as a host. As a matter of fact, Nik Collection runs fine from Affinity Photo MAS as well, but I keep having issues with other plugins, not Nik related, whilst they run fine in AP Serif.
Note: These instructions only work, if the folder where you install Nik exists. If you do a fresh install or if you uninstall an old version and then install a new version, you have to create that folder first, otherwise you will not be able to pick it during installation and thus do not see Adobe Photoshop Custom1.
Also, please note that Nik Collection 4 does not support M1 machines natively, so either you force Affinity Photo to run in Rosetta 2 (which makes no sense) or you do your Nik work separately and bring the results in on a separate layer. Disappointing that Nik Collection 4 does not support the Apple Silicon code base.