Most cinemas and showtimes are now back to normal, with a few exceptions, and Alamo blames its Sony projectors for what one cinema called a "nationwide" outage.

"Due to nationwide technical problems with Sony, we can't play any films today," read part of a paper sign stuck inside a Minnesota location.

However, one customer snapped a picture of that sign after watching The Apartment at that same cinema.

"When we got to our seats, the staff told us that even though the previews were playing, we wouldn't know until the film started if we could see it or not. If it didn't work, the screen would just go black. Luckily, the film played without a hitch," he wrote.

There are rumours that out-of-date digital certificates might have caused problems unlocking encrypted films. 

There is a secret code used to make all films distributed by Deluxe," and this ran out on December 30.

"This means that nearly all Hollywood films will no longer play on many commercial cinema servers. In particular, many showings of Wonka and Aquaman had to be scrapped due to the out-of-date encryption code," one Slashdot reader said.

Deluxe and the film companies have been trying to remake and send out new versions of current films over the last few days. People are still determining what will happen to older film titles since everything made by Deluxe since 2011 might be a hit and need to be remade if it is to be shown in cinemas again.