Android app no longer working

More precisely, it's working at a bare minimum: calculating routes, displaying them and – usually – tracking my whereabouts. But at that level it's simply like my old Etrex with a better screen. What it's not doing is: 

• Giving voice instructions
• Giving on screen turn instructions
• Dimming between turns
• Re-orienting the screen at turns, or indeed orienting it when starting. 
• Sounding the off-route klaxon

This happens regardless of whether I use the "Where to?" or the "Plan" button. Activating "always access location" makes no difference, and I can't work out what the "Follow" button is doing, if anything, but the useful functions do seem to have disappeared at about the same time those two changes were introduced; maybe that's just coincidence and I wouldn't swear it was exactly the same time.

This is on a Motorola Moto E7 running Android 10.