Automatic updating failed in several Early Access builds (as mentioned in the release notes), you needed to download and install the Roon update manually.
I assume you can download and install the latest build (uninstall the older build first, before installing the newer build) from the Roon 2.0 Build 1268 page now, since the link to the separate download is not added anymore. (But not sure)
Roon updated automatically from Roon 2.0 Build 1257 Early Access to Roon 2.0 Build 1268 Early Access without problems on my system(s).
Roon 2.0 Build 1268 is Live! - Early Access / Software Release Notes - Roon Labs Community