If you've become disconnected, please be aware you will not receive an email from BMW to follow to reconnect. You will need to manually reconnect through your BMW connect account.
Head to BMW ConnectedDrive
Sign into "My BMW" in the top right corner
After logging in, click on the "My BMW" icon again and select "My vehicles"
You should then see the vehicle and an option below, simply called "BMW"
Select that option and scroll down until you see "By Miles" in the data permissions section. Here you will be able to grant access.
Your By Miles app should now confirm that you are connected.