Some games don't link to specific store page

They might well be games that got kicked off Steam because of dodgy developers, licenses expiring, etc. People can still make giveaways if they have valid keys even if something is gone from the store.

I've had a problem with loading some store pages. It started recently and have had to reload the pages several times to get it to work. It has nothing to do with removed games.

There will be some cases where a game has been removed or it is simply not listed for your region on the store. But there is definitely something else going on lately with games that are still available.

When you stumble upon such removed game, but still want to get info about it (some removed games are actually worth playing!) then just copy the not-working store link (https://store.steampowered.com/app/xxxxxx/) and replace the domain "store.steampowered.com" with "steamcommunity.com". This way you can check its Steam reviews, screenshots, discussion pages, etc.

You can use SteamDB in that case.

It also happens if the game in Question is not sold in your country

May I suggest you some of my scrips to help with this issue:
https://greasyfork.org/ru/scripts/27887-redirect-removed-steam-id-to-steamdb
https://greasyfork.org/ru/scripts/39492-steam-error-widget-helper