I’ve found the older thread about Kerio. Newer Spark-Versions don’t work right
In short, Kerio is a very old rebranded version of Tigase server, which doesn’t support xmpp well. It worked with older Spark version. But as Smack library was updated in Spark, they can’t talk to each other normally anymore. So, either Kerio should be updated to support features or Spark should go back to old version of Smack, which is not an option. Or you can continue using 2.7 version.