Starting with Mac OS 10.15 all installed apps must be notarized. Maple 2019.2 will be fully supported on Mac OS 10.15 as a notarized application.
As a workaround for Maple 2019.1 and older versions of Maple you may be able to run the installer as the administrator. Right click to open the options menu (Control + click) and select Open to run the installer.
Follow the on-screen prompts to complete installation or see our general installation instructions from the Documentation Center.