Login screen almost too small to read

New Zwifter here. After installing Zwift on a Dell laptop with 3840x2160 native resolution, the login screen takes up a small fraction (less than half) of the screen making the font in the login box almost too small to read. There is no “make it full screen” icon in this window, only the ‘X’. Once Zwift starts, the display goes to full screen and all is good. Only the login screen is the problem.