There are certain themes when declare custom post, they used to do this:
And when it happens, the "Step 3: Title & Meta" in Infinite SEO will not show the aforementioned custompost.
After some searching, I found a solution to this:
in line 917 of wds-core/wds-onpage-settings.php, change to this:
add_action( 'init', 'wds_seoopt_settings' ,50);
All the missing custom post type and taxonomy will appear.
I guess it make sense to assign the priority of the action lower in order to capture all custom posts and taxonomy created by themes.
Hope you would commit this into your future updates if it doesn't cause other bugs.