Hi, soldierx -
Welcome to Apple's Discussions.
SimpleText may not be able to use that service when OS 9 is used within SheepShaver, since that is an emulation type program.
However, in case it may be able to, make sure that these items are enabled in Extensions Manager -
• Control Panels -
Sound
Speech
• Extensions -
Sound Manager
Speech Manager
In addition, there should be a folder named Voices in the Extensions folder, with at least one voice file in it.
If you are missing any of those items, re-install the appropriate language (English or Spanish) Speech-To-Text from your OS 9.0.4 Install CD.