Can I get a refund or credit? I bought at CostCo Intuit Turbotax Premier Federal State 2024. I see I bought by mistake a Download for Win/Mac. I use Chromebook.

You might see if Costco will give you a credit or refund if the product is not used and unopened. That's where you bought it from, not TurboTax.

Try Costco first, since that may be the easiest, but they might not do it.  Some users have had luck with Costco, while some haven't.   Tell Costco you don't have a computer to install it on.

If Costco will not refund it, you can get a refund directly from TurboTax with the online submission form.  

Scroll way down in the FAQ to the interface for the online refund request form. 

FAQ:  How do I request a refund for my TurboTax product?

https://ttlc.intuit.com/turbotax-support/en-us/help-article/intuit-refunds/request-refund-turbotax-product/L834M6uyW_US_en_US