No. When you first connect your Xero organisation to Xenon Connect it pulls in all of the required data from Xero.
Then, each night, Xenon Connect pulls in any new data and changes to Xero data automatically.
The only reason that you may choose to use the manual sync buttons is if you have processed a lot of data in Xero that day and you can’t wait until the next morning to view the effect of the changes in Xenon Connect.