A piece of content you can see everywhere else is not in your store. This happens constantly and the causes are usually mundane, so it is worth working through them in order before assuming something has gone wrong.
Region restrictions
Some content is legally restricted by territory. This is common for content involving local regulation, for region-specific store licensing, and for anything whose licensing terms differ by market. The restriction is enforced by the platform, not the publisher, which is why the content simply is not visible to you rather than showing as unavailable.
If the store page you are looking at is a different regional storefront than your account, the content may exist and still not appear.
Platform exclusivity
Console exclusives and timed console exclusives mean the content exists on a platform you do not own, or on the same platform after a window. Both are contractual and both are published in advance.
Account and region mismatch
Your store account region has to match your payment region and often your actual location. If you have moved, changed payment methods, or travel regularly, a mismatch can hide content. This one is resolvable and the fix is usually in your account settings rather than anything the publisher controls.
What to do
Check the publisher's own support page for the content by name. If they list a region restriction, that is your answer. If they do not and it is still missing, it is worth a support ticket, because that is a genuine problem on their side.
What is not worth doing is working around a region restriction. Beyond being against terms of service in most cases, region locks usually exist because content was licensed differently per market, and circumventing that puts you in the wrong market legally rather than just technically.