Why is my Shopify product active but unavailable to customers in one country?

If it’s available everywhere except one country, check the market catalog before changing the product’s Active status. In Shopify admin, go to Markets, open that country’s market, and check which catalog applies and whether the product is included. A product excluded from the market won’t show in that market’s store search, and a direct product URL can send the shopper back to the homepage. Also check the product details page: it still needs to be available to the Online Store or whichever sales channel the customer is using. Products > View as is a handy way to see the result for that market; excluded products show as Unpublished there.