The new 9.4xx Navcore (and some older V9 as well) will cause many XL models to go silent when computer voices are used,
a few won't even play recoreded voices anymore.
There is a very simply check that you should perform if you think you are affected:
Make a full backup using the Windows Explorer (safety first! ),
connect to TT Home and check if you can download any computer voice for your device - you might have to log in to your account for that.
If Home does not offer you any computer voice it means that your device has no offical support for TTS.
Spoiler: Show
Since you bothered reading this I have to assume that you already tried some Navcores and your device still wont talk to you
Go to the Navcore section and check my 9.485 thread.
Read the info and instruction carefully!
Choose the version that suits your model and in 99% of cases you will get everything working that you need and your models can support.
Update: All my installers now support the XL models, so please use the Universal Navcore Installer for the latest Navcores.