Before connecting your Google Express account you should create a channel. Since Google Express requires a storefront it should be added as a subchannel to your store.
1. Go to Menu > Settings > Channels
2. Click Add Channel on the upper right-hand corner
3. Select Google Express
4. Choose the Country
5. Name your channel
6. Click the Create button
7. Enter your Google Merchant Id
8. Click the Save button
*** Please add the following user name to your user list and give all available access rights to StoreAutomator at Google Merchant Center.