Any solution for that? Got the same problem on one of my MBs
You need to use a full installer for the update. I had to use the one from Beta 3 and then the update worked. Same for someone else here.
Now there is a full installer for Beta 4 and you can try using that to update:
Download and run the InstallAssisant (15.59GB), it will put a "Install macOS Sequoia Beta" app (15,64GB) in the Applications folder, what you can use to update.