The play back speed of my captured macro cannot be changed to play faster

Does the macro you captured contain any Delay commands? The Macro Playback Speed only affects the Delay commands in your macros. For example, if you have a Delay of 486 milliseconds and you are playing the macro back at 10 times the speed, the Delay command will only wait for 48 milliseconds (486 / 10).

Macros can be captured without any Delay commands. If the ‘Capture At’ option in the Capture Settings is unchecked, no Delay commands will be inserted into your macro. If there are no delays then the macro runs as fast as your computer and Macro Express can play it. But, a macro without any delays will run so fast that your system may not be able to keep up. If this occurs, the macro will not play back correctly.