MIT indicates Navigate should be fixed in the version available on TestFlight.
MIT App Inventor for iOS Version 2.64.6 in TestFlight App Inventor for iOS . You could test the distance and route aia using the advice in the link above or wait for for the problem to get fixed on the main ios server with a future update, hopefully soon.
Try using the TestFlight Server using the Navigate aia while waiting for MIT to release an updated ios Companion. Let us know if using the TestFlight version works for you.