For a real offline experience, must use offline maps and select a single offline routing service.
(with Kurviger 1.13.16 (Beta) - #151 by devemux86 that’s more convenient)
Anyway without a route example (and user location), it’s difficult to understand what happened.
Regarding voice guidance, each phone & headset work differently.
Can test app settings like audio output and see the documentation:
(here and here)
Have you changed recently any Android or headset settings?