Calxa will send an email if the daily sync fails. Sometimes this is because the user who connected the Accounting File to Calxa, is no longer a valid user on the Accounting File.
Navigate to: Settings > Organisation Settings > Organisation Sync
Review who the file was connected by
If they are not a current authorised user
Click the overflow menu (...)
Disconnect the file
Refresh the screen (Ctrl+F5 keys together)
Click the overflow menu again
Reconnect to your accounting system, using active credentials
Check the Daily Sync Settings in the same overflow menu
Ensure that notifications are being directed to a current user