When you publish an app in the Google Play store, Google expects that app to be signed with a certificate. When you create an Android app with Twixl Publisher, we take care of creating this "keystore" for you in the background. Every update of your app will have to be signed using the same keystore information (the app's "fingerprint" so to speak), otherwise it will not be accepted on Google Play.
The keystore information will be saved as part of the build setting for that app. This means that, if you migrate to a different machine, you will have to make sure to also migrate the build setting.
Either use the option "Export Developer Identity" from the 'Tools' menu in the Twixl Publisher application, or right-click on a build setting to reveal it in then Finder and copy it manually.
Note that if you ever lose the keystore information, there is no other way to retrieve it, you will be unable to update the app in the future.
However, we have changed the behavior for new build settings created with version 4.2.2 or higher: a keystore is now generated once for your account (based on your account ID) and is used for all new build settings. That way, all build settings will be using the same Android keystore.
Migrating your Google Play app from another platform, such as Adobe DPS, etc.
If you are moving to Twixl Publisher from a platform like Adobe DPS, you will have created an Android keystore using the Keytool via terminal, according to the instructions outlined in Adobe's documentation.
During that process you generated a keystore with an extension ".p12". In order to update your existing Adobe DPS app to an app created with Twixl Publisher, you can use the 'Import' option in the Code Signing tab of the build settings for that app. When importing the .p12 keystore, you will also need to provide the password you used to create it.