Issue:

After a user or Administrators downloads and runs/installs screen connect on a mac you only see the top toolbar and a black screen.

Solution

1. On the Mac Click Open System Preferences.
   1a. You may need to click on the Finder and type in 'System Preferences.'
2. Click the Privacy tab or the Security & Privacy icon (Figure 1).
   
   Figure 1:
   
3. Click the Lock icon in the lower left-hand corner of the window to unlock the Privacy Settings (Figure 1.1).
   
   Figure 1.1:
   
   3a. You may be asked to enter the Administrator Username and Password of your Mac in order to proceed.
   3b. Use the same username and password you use to unlock your computer after a restart.
4. You may be informed that ScreenConnect needs to be Quit and Reopened after updating settings. If so, click Quit & Reopen (Figure 2).
   
   Figure 2:
   
5. Once re-opened, you may get another prompt asking to Open System Preferences, if so, click Open System Preferences (Figure 3).
   
   Figure 3:
   
6. Scroll down to Accessibility in the left-hand menu and click it. This should populate ScreenConnect Client to the right-hand side of the window. Place a check mark next to ScreenConnect Client (Figure 4).
   
   Figure 4:
   
7. Once ScreenConnect Client is checked in Accessibility, you will want to repeat the process for the Screen Recording tab.
8. Scroll down to Screen Recording from the left-hand menu and highlight it. This will populate ScreenConnect Client to the right. Place a check mark next to ScreenConnect Client (Figure 5).
   8a. You may get prompted to Quit and Reopen. If so, choose this option and proceed with the steps once it is reopened (refer to figure 2 above).
   
   Figure 5:
   

Solution has been referenced from :

Unable to ScreenConnect with Mac | Help - Illinois State