This can happen when the Xero account password is changed, the authorisation is revoked in Xero, or the token has naturally expired. To fix it, go to **Access → Apps → Company Settings → Integrations, look for XPM and select Disconnect, confirm the disconnection, and then select Connect again. Once reconnected, the client sync will resume automatically. If the connection fails during the re-authorisation process, check that you are signing in with the correct Xero Practice Manager administrator account and that ChangeGPS is listed as an authorised application in your Xero account settings.