Thanks everyone for your input on this issue! My apologies for taking so long to get back to you about it.
After some investigation, it appears that the issue stems from a bug in the search function of the Software store (version 3.28) in Zorin OS 15, which sometimes causes inconsistent search results. Different variations of the “Zorin Windows App Support” search query (like “Windows App Support” or “Zorin Windows”) might display the correct result while other variations won’t. This might even vary from session to session (i.e. after closing/killing the Software store and opening it again).
It doesn’t appear to be related to Amazon EKS, which is just a listed app in the Software store.
I’m currently running a pre-production build of Zorin OS 16 (for development) and can confirm that the search function in the newer Software store (version 3.38) is working correctly and is displaying the results much quicker and more reliably. Every variation of the “Zorin Windows App Support” search query displays the correct result at the top of the list, and in every session.