The July 1 issue of the Monthly Notices of the Royal Astronomy Society includes an article evaluating the standard multiverse prediction of the cosmological constant, with result:
The predicted (median) value is 50–60 times larger than the observed value. The probability of observing a value as small as our cosmological constant Λ0 is ∼2 per cent.
If your theory only makes one prediction, and that prediction is off by a factor of 50, that’s the end of it for your theory. I’m very glad that this has now been sorted out, the multiverse hypothesis has been falsified, and theorists who have been working on this can move on to more fruitful topics.
Update: As David Appell realized, the last sentence here was sarcasm (or maybe black humor). Those promoting the multiverse are doing Fake Physics™, not Physics. This is ideology, not science, and there is no chance that they will stop referring to the “successful multiverse prediction of the CC”, no matter what analysis shows a seriously incorrect prediction.
As Blake Stacey points out, this paper was on the arXiv back in January (see here), and has just been ignored by multiverse proponents. Part of doing Fake Physics™ is ignoring any information that contradicts what you want to believe. Another commenter points to this 2014 argument from Sesh Nadathur, which similarly as far as I know has just been ignored.
After appearing on the arXiv in January, this latest work was promoted by press release from Durham University back in May, which led to lots of media stories (e.g. here). For some reason, the press release didn’t really explain that this work falsifies the usual claim that the value of the CC is evidence of a multiverse. Instead, the work was promoted as showing that the multiverse is “more hospitable to life” than thought, which sounds good I guess, but seems like a bizarre way to explain the significance of this work.
For various sensible explanations of what is really going on here, see Jim Baggott, Philip Ball, and Sabine Hossenfelder. I’ve often repeated my own version of how to see there’s a problem with trying to explain the CC this way. There is no actual multiverse theory, so proponents assume a “flat measure over the anthropically allowed region” and then calculate. This is exactly the same input as my theory of the CC, which is that I have no idea what is going on, so any value is equally likely. The bottom line from the latest work on this is that, even if for some reason you believe you can get a sensible “prediction” this way, the prediction comes out wrong.