I have updated to the latest version and created brand new Invisible v2 keys. Also selected Invisible from the general settings menu. Everything seems to be verifying correctly and the badge does appear where it should on the page.
Nevertheless, on two different sites, I always get the same error: “the recaptcha was invalid”
While official GF Support does reply here rather regularly, in it’s base these are the Community Forums and not the official Support channel. Have you contacted Support through the official channel by opening a Support Ticket?
No, as I assumed that the new implementation was simply not working correctly since the same error is appearing on two completely different sites with different themes…but I will now!