The ability of Kiora, Sovereign of the Deep is no longer working correctly. It seems to be the same issues that has been around 2 years ago which became broken again.

Instead of opening the browser with the top X cards of your library these cards are highlighted on your library. You can't choose any of those to play. All you can do is choose to "Resolve" the ability without casting them, making Kiora useless.

Here a link to a 2 year old thread in reddit to the bug that just came up again.
https://www.reddit.com/r/MagicArena/comments/13ya22u/kiora_sovereign_of_the_deepbugs_that_arena_devs/