An issue has been identified with DWA 126.96.36.199 causing backup failures. The fix is now available and agents will auto-upgrade to 188.8.131.52 over the next 12 hours.
The 184.108.40.206 installer is also available for download if a more immediate fix is required. NOTE - Neither manual nor auto-upgrade from 220.127.116.11 to 18.104.22.168 require a reboot: https://www.datto.com/downloads/legacy/DattoWindowsAgent.exe
Please bear in mind that you can also force a 22.214.171.124 system to auto-upgrade via one of the methods below (may take up to 5 minutes):
CMD: net stop DattoBackupAgentService && net start DattoBackupAgentService
Powershell: Restart-Service DattoBackupAgentService