A week ago I'm trying to migrate the contents of K2 version 1.5 to 2.5
I bought two extensions that do not work. (DM K2 XML Exporter and Import for K2)
And support the extension JUpgrade is garbage, you download the extension for free but have to pay a fortune to solve the bug of extension.
Their support is unresponsive and inefficient, the don´t aswers my question.
I need to change 10 years of content from one to another joomla and so far only lost money.
None of them work right.
Can you help me?

I do not recommend the k2, if I knew that would just never have played my part in this content.

Moving from 1.5 to 1.5 is not fun for sure. Have you tried this
getk2.org/documentation/tips-a-tricks/item/311-manually-migrating-k2-content-from-joomla-15-to-17