Problems formatting USB stick for MinimServer install

[paynni]

I have been trying to format my USB stick so that I can reinstall Minimserver on my Melco N1ZMk1. I go through the procedure you outline on your website (where the stick is identified within DOS). It then asks for my password. However, on my Mac all I can see is a vertical “key” shape within a box which does not allow me to input my password. I have seen this before and after repeated attempts I have been able to input the password and continue. However, seemingly I can no longer do this and I can’t produce the USB to load the program onto the Melco. Any ideas? My Mac version is OSX El Capitan Version 10.11.6.