Our support team has seen this a few times in larger production installations, and we are investigating. So far however, we have had problems reproducing this issue consistently or determining the root cause.
I did look at your CSV and I also don't see anything there that would lead to this kind of error. I would advise you to follow Jim's suggestion and try rebuilding the nested set - and also repopulating the search index. Might as well clear the application cache and restart PHP-FPM as well, to ensure you are not seeing any cached results returned. I think it would be important to confirm whether or not the import simply doesn't run at all or whether the records exist in the database but don't display in the UI because building the nested set and indexing them fail.
Make sure when you review the site that you are logged in (in case the records are draft), and also clear your web browser cache or else test in a private/incognito browser window. If they don't show up after running those maintenance tasks etc, then I suspect that the entire process is simply failing to launch the import.
We are tracking this issue internally and doing everything we can to get to the underlying issue and resolve it for 2.7. It doesn't seem to happen consistently, so if you perform the above maintenance tasks and review and find no records, you could try the import again and it will likely succeed.
Dan Gillean, MAS, MLIS