Your email address allows you to log on to the Hub and the App. The email address is strongly linked to the security on the App, so there is a specific process to follow to ensure that after changing your email address that all work under the old one is associated with the new one.
Synchronise each account in the App separately and fully
Don't start synchronising an account whilst a sync is already in progress
When all syncs have reported back 'Sync Finished' and no errors / resyncs are required you can uninstall the App.
Find the App in Playstore - you will see an 'Uninstall' button
Log on to the hub using the existing (old) email address
Click on the 'Profile' button in the top right.
On the profile page, enter the new email address (1), and your current password (2), Click on 'Update'
A confirmation email will be sent to the new email address
Click on the confirmation link in the email
Install the App from Playstore
Log on with the new email address
The sync will start automatically and fetch all active work