Forum OpenACS Q&A: Re: No Option for Automatic Upgrade for OpenACS 5.1.5 to 5.2.x

The repository, which downloads the code you for, does not support upgrading the minor version, only the patchlevel.

You need to use the acs-admin installer and upgrade from the filesystem.

https://openacs.org/doc/openacs-5-2/upgrade-5-0-dot.html

and make sure to test it first on a copy of your production machine.