kronos1 wrote: ↑
Thu Jun 13, 2019 7:12 pm
"NuCaptcha v1.x was sunset in 2018, and the supporting infrastructure was decommissioned earlier this week."
Not great news, but at least helpful for explaining the "suddenly stopped working this week", and provides confirmation that the failure has no bearing on why Google reCaptcha also doesn't work for you. i.e. It's not because of a PHP hosting change on the server affected communication by both plug-ins; the Nucaptcha failure was uniquely Nucaptcha.
The PHP error log settings shown would make me check whether my Apache error log was receiving the PHP errors. If you talk to your hosting provider about anything else, maybe asking them about where you can expect to see the PHP errors would help point you to where they're at in your particular hosting account.
Since you didn't seem to know what the source of the Google reCaptcha v2 keys was, maybe its also worth requesting your own new set of v2 keys and making sure that doesn't solve the reCaptcha failure? e.g. Maybe reCaptcha is failing to report what is actually some kind of expired or disabled key situation, or keys that were created for a different domain name, for whatever apparently unknown set of keys were currently entered in the phpBB Spambot Countermeasures configuration for the reCaptcha plug-in on your site. Since you made it sound like "all you had to do was select it", without having to first configure it with API keys.
If the issue continued, my own next step would be comparing for file differences & disabling extensions, in an attempt to determine why "reCaptcha v2 works fine in phpBB 3.2.7, but not on my site." But understandable if that's not an extent you have time or are willing to pursue at this time. Making a copy of your site to a local XAMPP installation and investigating it that way (without interrupting the live site) is also an option.