For years I have been using self made macros that simply copy a highlighted portion of text, open a Safari window and paste it into my homepage's search field. I hereto defined a dedicated KM clipboard.
Lately every such macro stalls upon pasting. The macro fires properly, opens the Safari window just fine, then nothing happens. I inspected the dedicated clipboard and even this one shows the right, freshly copied content.
KM 7.3.1. on macOS Mojave 10.14.6 (updated recently, maybe it has to do with it...?!?)
Accessibility access to control your computer is required to use many features including selecting menu items, manipulating windows, pressing buttons, typed string triggers and the window switcher.
You will need to enable Accessibility permissions for both Keyboard Maestro and Keyboard Maestro Engine.
On modern macOS, you enable Accessibility permissions by opening System Preferences, going to the Security & Privacy preferences, and in the Privacy pane select Accessibility and ensure that both Keyboard Maestro and Keyboard Maestro Engine are ticked.
Note that for Catalina continues the tradition started in Mojave of being difficult with the Accessibility permissions, and I have several reports of people having troubles enabling accessibility for Keyboard Maestro Engine. You should report this to Apple using the Feedback mechanism. Remove the Keyboard Maestro Engine entry from the accessibility permissions, then quit and relaunch the Keyboard Maestro Engine (in Keyboard Maestro, File ➤ Quit Engine, File ➤ Launch Engine) to re-add it, and then you should be able to enable it.
Note that for Mojave it is fairly common for the accessibility checkboxes to be on but Keyboard Maestro still not have permission. Generally toggling the accessibility permissions checkboxes off and on resolves the issue. Alternatively, deleting the entries and letting the system re-create them usually works if toggling is not sufficient.
If you continue to have problems with enabling Accessibility permissions, ensure you only have one copy of Keyboard Maestro on your Mac, that it is in the /Applications folder, that you moved it there using the Finder and restart and try again.
If you continue to have problems, you can use the tccutil reset Accessibility command to reset the Accessibility permissions.
Note that for Catalina continues the tradition started in Mojave of being difficult with the Accessibility permissions, and I have several reports of people having troubles enabling accessibility for Keyboard Maestro Engine. You should report this to Apple using the Feedback mechanism. Remove the Keyboard Maestro Engine entry from the accessibility permissions, then quit and relaunch the Keyboard Maestro Engine (in Keyboard Maestro, File ➤ Quit Engine, File ➤ Launch Engine) to re-add it, and then you should be able to enable it.