I recently started upgrading one of our sites, that has over 4,000 pages, from Joomla! 1.5 to 2.7. I have been able to get all the articles into 2.7, but the K2 import is not working, which I have been able to do without issue on about 15 other sites. When I go to do the import, the categories come over correctly, but not one articles comes over into K2 and I do not get any error messages, just a confirmation message.