Games published by Sony Interactive Entertainment are no longer available for preorder on Amazon. That includes many anticipated exclusives for Playstation 4.

Customers noticed the change in April, around the time that "God of War" was released.

Amazon usually courts gamers with perks like 20% off preorder titles for Prime members.

Nobody — not even Amazon customer service — seems to know what's going on.

Gamers can no longer preorder some hotly anticipated Playstation 4-exclusive games on Amazon.

Instead of a preorder link with a price, like other games on Amazon's website, these titles — all published by Sony Interactive Entertainment — just state that they are "currently unavailable." A note underneath says, "We don't know when or if this item will be back in stock."

The games are some of the most hotly anticipated games of 2018 and include most Playstation 4 exclusives, like "Detroit: Become Human," a game set to be released later this month, and the new "Spider-Man" game, which isn't due to be released until September.

Customers started noticing the change in April, around the release of the new "God of War" game. The game suddenly became unavailable for preorder in the week before it was released. The game did become available for purchase from Amazon on release day. The preorder issue does not seem to affect already-released games.

The removal of the game's preorders has previously been reported by video game blogs like Eurogamer.

Nobody seems to know what caused the sudden change. Some customers speculated it could be a stock issue, but a quick glace at competitors like Best Buy, Walmart, and GameStop shows that they are all still offering preorders of the games.

Business Insider reached out to both Amazon and Sony for comment, but neither company responded. According to customer complaints on social media, Amazon's customer-service team did not seem to be aware of the issue.

Some customers have been frustrated about the lack of preorders, as Amazon offers a generous 20% off for Prime members preordering video games on the site. Customers who already preordered games before they became unavailable on Amazon are now left to wonder whether they'll even get the games they bought.

"I preordered Spiderman PS4 back in August from Amazon and it's visible in my order history but when I click order details the page is just empty," one Reddit user said.