When I try to install the macOS public beta it opens system preferences after I install it and a pop-up says "The requested version of macOS is not available." Please help me with this
        
      
      
    macOs Big Sur Public Beta
        
          the same problem 
        
      
      
    
        
          have found solution 
So I ran sudo as root via terminal and typed the commands there:
open terminal
sudo -i
enter root password
/System/Library/PrivateFrameworks/Seeding.framework/Versions/A/Resources/seedutil
Unenroll from the Beta Program
/System/Library/PrivateFrameworks/Seeding.framework/Versions/A/Resources/seedutil unenroll
Enroll in the DeveloperSeed Beta
/System/Library/PrivateFrameworks/Seeding.framework/Versions/A/Resources/seedutil enroll DeveloperSeed
Close and re-open System Preferences > Software Update
The new Beta should now show up
        
      
      
    So I ran sudo as root via terminal and typed the commands there:
open terminal
sudo -i
enter root password
/System/Library/PrivateFrameworks/Seeding.framework/Versions/A/Resources/seedutil
Unenroll from the Beta Program
/System/Library/PrivateFrameworks/Seeding.framework/Versions/A/Resources/seedutil unenroll
Enroll in the DeveloperSeed Beta
/System/Library/PrivateFrameworks/Seeding.framework/Versions/A/Resources/seedutil enroll DeveloperSeed
Close and re-open System Preferences > Software Update
The new Beta should now show up
        
          This works for me