I can no longer use F10 to activate a macro.

You should be able to use the F10 key to activate a macro. The ability to use this hotkey for a macro does not depend on the version of Macro Express or Macro Express Pro that you are using. It does depend on the version of Windows that you are using. The dialog used to select a HotKey has been improved to display more information about which HotKeys are Reserved and/or Restricted by Windows.

Note that the warning message that is displayed when you choose F10 as a macro activation says “Using this Hotkey for a macro may cause some features in Windows to not function. Would you still like to assign the HotKey F10 to a macro?” Note the word “may”. You should be able to use F10 to activate a macro but the Windows feature that uses F10 will not longer function by pressing F10.

Microsoft has been reserving more HotKeys for exclusive use by Windows.
Hot keys designated as Reserved for Windows are used by Windows for specific functions, but may be overridden by Macro Express. For example, Ctrl + C is used to copy highlighted text to the clipboard, but the key may be assigned to Macro Express to perform a different function.

Hot Keys shown as Restricted to Windows are reserved by Windows for its own internal use. Depending on the version of Windows being used, these hot keys may not activate Macro Express macros. They will only perform the function assigned by Windows.