The profile setting "Hide Games with no achievements" was filtering them out.
Though you don't need to revert this setting. I made some changes to ignore it, on the imported games.
They don't technically have real trophies on the backend (only linked to the PSN equivalents) so that's why it was impacted by this filter. I'm not sure whether some recent changes caused this or if it's always been an issue - either way, fixed now. Thanks for reporting it.