Actually it’s not a simple problem — the database structure has changed (the post2cat table has been added; not sure what else) since this importer was created and it just plain don’t work.
I got fed up and rewrote it. Mine is ugly as hell, but it WORKS… at least on my install. ??
Caveats: I had only one author in both blogs. I cleaned out all the default categories and sample posts & comments in WP before importing. (In phpmyadmin, I emptied the following tables: wp_categories, wp_comments, wp_linkcategories, wp_links, wp_post2cat, wp_posts. If you have stuff already entered in WP, do back up before trying this.)
My importer missed the very last post to TXP, but it handles posts, comments, categories, links, and link categories… so I didn’t mind copying the one post. ??
If you’d like to try it, download https://sillybean.net/tools/import_textpattern2.zip. Unzip, fill in db info for BOTH databases, upload, and fire away.