Hi, I can't get it to work on the current site. But I spun a new test site and was able to get the Screen Options updated on a MB CPT.
There was possibly an issue with one of the taxonomies associated with the CPT. I was using a taxonomy slug "type" and it wouldn't work when exporting to another site. So I spun up a brand new site and tested that tax slug with CPTUI plugin. It gave me an error: "Please choose a different taxonomy name. type is already registered." Default 2021 Theme and no other plugins.
I tested with MetaBox and it didn't show any issues with that Taxonomy slug.