OneDrive does not automatically synchronise files. Each team that you would like to synchronize needs to be manually added. However it is a simple process.
1. Open the Team in the Teams App and click on the General channel.
2. Click on the Files link in the right hand window
3. Change to the All Documents level by clicking on the word Documents to the left of General.
4. Finally press Sync to synchronize all channels in this team via OneDrive