[NSFW] Not using Avada 404 template correctly or redirecting to 404 page

Hi,
I marked the topic as mature as the site does sell medical devices related to fertility.

I recently installed v1.9.16.6 (latest) on my site. It uses the Avada theme and I use their layout feature to create a 404 page. (see here: https://timmmedical.com/404).
I noticed that when WPS is enabled, the registration page on the site does not use the 404 template correctly, omitting the styles required on the page, nor does it redirect to the 404 page. Within settings, I have the redirection URL set to “404”.

Kindly please advise on what can be done to fix the issue.
Thanks!

The page I need help with: [log in to see the link]