Can you tell us what operating system you're using?  WIndows 10?  macOS 10.14?  CentOS 8?  I vaguely recall reading about an error typing in @'s that was in the user interface toolkit ChimeraX uses, but I thought it didn't affect the version ChimeraX is using.  It will be good to track this down.

    -- Greg

I would like to register ChimeraX but I cannot enter @ in the box for my email address. Instead, the @ appears on the command line. 

Best regards

Raymond Cox

University of Southern Denmark