I have just checked the faqs for the app and it does say that you shouldn’t delete and reinstall the app. If any problems are encountered in the process they suggest you contact them by e-mail at connectedservices.support@honda-eu.com or by phone on 0345 200 8000.
Another thought is whether the app is still active on your previous device. If so that would be the primary device for the account and it might possibly be waiting for you to verify the new secondary device on the old one. If you have deleted the app from your old device then it looks like you will have to contact connected services as above.
Hope this helps