Edited. It now accepts KATERINA as well (on English side).
Though if you are serious about learning Czech you might be better off installing the czech keyboard on your computer and switching to it.
It is accepted. If your answer was not accepted and it should be, use "My answer should be accepted". If you discuss it here, always report the complete sentence.
"Did you return Katerina's pen?" is not accepted. I am assuming the pen belongs to her, but does her ownership of the pen make a difference?