KeiKai OSE is not supported to work with ZK 10 (work with 9 or before). Please change to KeiKai EE.

Breeze, Sapphire, Silvertail, and Atlantic are also no longer supported since ZK 10.
If you're currently using Breeze, Sapphire, or Silvertail, we suggest migrating to the iceblue_c.
If you're using Atlantic, we suggest migrating to the iceblue.

Please see

https://www.zkoss.org/wiki/Small_Talks/2024/February/New_Features_of_ZK_10.0.0#Unsupported_Themes:\_Breeze.2C_Sapphire.2C_Silvertail.2C_and_Atlantic