When moving my test environment from Apple Intel (Zenphoto 1.6.4 on Ubuntu 23.04, PHP 8.1.12 under VirtualBox 7.0.14) to Apple Silicon (Zenphoto 1.6.4 on Ubuntu 24.04, PHP 8.1.34 under VirtualBox 7.2.12 - I didn't get warm with MAMP), I received the error message “A configuration error occurred, please return later” when I first launched Zenphoto. The database login credentials appeared to be correct in ../zp-data/zenphoto.cfg.php.
After a few unsuccessful attempts, I renamed that file — but didn't delete it — in the hope that it would be rewritten during installation. Note: I knew the login credentials. That was the solution, and the installation started. Afterward, I compared the contents of the old and new file:
old: conf['db_software'] = "MySQLi";
new: conf['db_software'] = "mysqli";
I'm not kidding!
Conclusion: If a configuration error has occurred and you know the database login credentials: try to rename the file ../zp-data/zenphoto.cfg.php and restart setup to enter the login credentials again. Setup will run as usual and the configuration file will be written with the correct login credentials.
I hope this helps someone who has the same problem as I did.

Have fun with zenphoto, cheers, imagepet