On Windows, this is most often the result of autoscaling. Please ensure any autoscaling on your system is turned off.
If you continue to have issues, this is most likely due to out-of-date graphics drivers. Download the latest drivers for your graphics card, then reload your computer and open BEAM again.
This can also result from a firewall blocking your DAW, which prevents BEAM from reaching its servers and results in the login screen being unable to load. Ensure any firewalls affecting your DAW are turned off.