Daily builds always take a break when a new version is released and are usually back within a week of release. According to a post on the Beta forum they may return starting tomorrow.
Graham Thompson, Technical Artist @ Rockstar Games
I hope they will fix the instability issues with V18.5. I get a lot of crashes opening up files created in Houdini 18.0 that have hda's. Fortunately, I can open them with older versions of Houdini without problems.