Hello Antonio,
The TSS_Library component is provided by a Sensor team (they have developed the library and the Processor Expert Component). You can post your question on the Sensor community (Sensors ) if you need details.
I have checked your application and I see following issue:
The TSS Config Register Init\System Configuration Register\LowPower Enabled must be set to yes. See below:

The TSI functionality in the VLLS3 power mode is restricted, see the description in the reference manual:
TSI module is fully functional in all of the stop modes as long
as TSI_GENCS[STPE] is set. The channel specified by
TSI_DATA[TSICH] will be scanned upon the trigger. After
scan finishes, either end-of-scan or out-of-range interrupt can
be selected to bring MCU out of low power modes.
You must also configure the LLWU device and enabled TSI0 as the wake-up source.
Best Regards,
Marek Neuzil