Since updating to the latest version of phpBB, it seems like the reCAPTCHA check in the registration process is no longer working. Due to this problem, nobody has been able to register on our forums for the last couple of days. Because Jesse Mynttinen reported the bug, I've switched the reCAPTCHA check to the 'simple image' check and tested the registration procedure. Everything should work fine now.
I've found a very recent thread on the official phpBB forums in which they talk about the same issue, so I will keep an eye on this. (https://www.phpbb.com/community/viewtop ... &t=2400996)