It could also indicate that you have no network active while driving.
Try starting the route while at home or on wifi and do a map refresh of the area as well. If it is network related, at least the first few roads should be cached and likely properly announced.
While you are driving, do you see any other wazers on the map or get any alerts? If not, it's likely network related.
In that case check that your data bundle is not depleted or that your APN settings are still 100%.
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