Transpose chord symbols

Welcome on board!
Chord symbols if properly inserted should be correctly transposed.
Maybe you could attach here your score?
use the "File attachments" option at the bottom of the page, just above the Save and Preview buttons when you're typing your post. Click on 'File attachments' it will become browse

What version of MuseScore are you using?

edit:
I see you say you used ctrl k, but it really doesn't look that way.
Sorry.

Your chord names are simple staff text.
You need to insert chord names with ctrl K as in the handbook.
https://musescore.org/en/handbook/chord-symbols

Please see my file; I've replaced the first line of text with actual chord names.
When you insert them correctly, they transpose as expected.