I am using PCB Editor 17.4. The workspace window size in 17.4 "S007" is so large, access to the OK button located at the bottom of the screen is blocked out.
This issue is reported in Cadence case “46450691” and it is being worked on by Cadence R&D.
For now, as a workaround complete the steps below:
1. Reset your monitor resolution to 1920 X 1080 ( Recommended )
2. Change the size of text, apps and other items = 100% Font size in Allegro = 8 default by using 'fontsize' variable in the Setup > User Preferences > UI >Fonts.