ABPro does not run under the current Joomla 4 alpha release.
Significant re-coding will required to get ABPro to run under Joomla 4.
This work has begun, and I anticipate no major problems with running ABPro (4.0.4?) when Joomla 4 finally arrives.
See an early ABPro 4.0.4 running under Joomla 4.0 Alpha 5 here
The above link to to a test site and may be broken from time to time, also additional ABPro functions will be added as the conversion progresses.