I’ll copy in an email I sent to @@justinb81 after trying out his CSV file. It may be useful in analysing the issue:
I’m getting an error that the post_excerpt cannot be null. I’m not sure why it is trying to insert a null into that column, but I’ll look into that. This could well be a change to the WordPress database. It could be I’m only seeing that specific error message because I have debug turned on, and you are just seeing the end result (skipped records) with debug tuned off.
Adding a “csv_post_excerpt” column allows it to import. Your file is UTF-8, without a BOM, and with Unix line terminators, so nothing unusual there.
The csv_post_date is not getting imported, so far as I can see. I changed it to UK/international style dates, and it is still not being imported. Another one for me to look at, assuming the column name is correct.
Could you try one thing for me: uninstall the plugin, then remove all its files. Then reinstall. WordPress does normally do this, but just in case any of the old files are being left behind, it will be worth trying this.