It is possible to sync ONLY ONE Bookeo user account with the same Google account.
If you have already set up a sync with your Google account, and want to sync a different Bookeo account, you will need to revoke the existing permission first, so that you can authorize the new Bookeo account to sync with your Google account.
To revoke an existing permission:
1. Click on the profile icon  at the top right in your Google account
2. Click on Account 
3. In the Sign-in & security section, click on Connected apps & sites 
4. In the Connected apps & sites section, click on MANAGE APPS 
5. Click on Bookeo 
6. Click on the Remove  button
7. When prompted if you are sure that you want to revoke the access, click on the OK  button.