If you do not receive any voice instructions on your Tour, this could be caused by an upgrade of your operating system.
In this case, please reinstall Google Text-to-speech. You can find and reinstall Google Text-to-Speech via the Google Play Store. After installing the app, you need to activate the app in the settings of your komoot app again: Profile (Head Icon) > Settings (Cogwheel Icon) > Navigation
It might also be necessary to log out of the komoot app and in again: Profile > Settings > Log out.
Before you do this, please note down the User ID and the mail address you find under Profile > Settings > Profile info.
After logging out and in again, you should be able to use your voice navigation again.