What version of Make are you using? What platform are you running on? Which version of Python do you have installed? What version of JUCE are you updating from/to?
Nothing in this part of the framework has changed recently.
@t0m@reuk Thank you for pointing me to the right direction.
macOS 12.3.1
GNU Make 3.81
(previously) Python 3.9.7
For some reasons, the default python symlink does not point to python3. I updated to python 3.9.12 and create new symlink to the updated python. And now ‘make’ build docs as expected.