Hello.
I have the exact same problem, and the update to 10.5 did not work for me. I am attempting to activate Polylang 2.5.3.
Reproduction Steps
1. Install and activate 404page 10.5.
2. Install and activate Polylang Pro 2.5.3.
3. Visit the user-facing web site.
Expected Outcome
The user-facing site should render with no errors.
Actual Outcome
The user-facing site displays a white screen. With error reporting enabled, error messages indicates a Polylang function doesn’t exist.
More info
I looked at the 404page code where the error is occurring and noticed the call to the Polylang function does not check whether it exists before attempting to call it.
