Problem during the installation of the new snapshot 20w21a

Hello, I have a problem during the installation of the snapshot in version 20w21a: When I'm right before the end, the installation stops, then it says that it couldn't download the version with the window opening (Have a look at the Attachment)

 

By the way I have not the 2.1.14932 version of the launcher, I have the 2.1.14948 one

 

Can I have help, please?