We’ve found a couple of issues with Copter-3.6 (see 3.6.12-rc1 release announcement here) so because we can only provide a single beta firmware at a time, Copter-4.0.0 will not available for download until next Monday (Dec 16th).
When it comes back next Monday Copter-4.0.0-rc3 will include several fixes though and we look forward to your continued help with beta testing.
If you’ve already got 4.0.0-rc2 loaded on your vehicle of course feel free to report any issues in this category and we will have a look, thanks!