XG Firewall Firmware Upgrade Failed: 17.5.16 MR-16 to SFOS 18.5.3 MR-3-Build408

Hello Ankit Na,

Thank you for reaching out to the community, when the upgrade fails is it going into failsafe mode?

Please refer the following KBAs below: 
> Reference points when upgrading to SFOS v18: https://support.sophos.com/support/s/article/KB-000038897?language=en_US
> Know the cause of hardware appliance going in failsafe mode: https://support.sophos.com/support/s/article/KB-000036375?language=en_US

Also log a support case, if it requires any further investigation. 

Hello Ankit Na,

Thank you for reaching out to the community, when the upgrade fails is it going into failsafe mode?

Please refer the following KBAs below: 
> Reference points when upgrading to SFOS v18: https://support.sophos.com/support/s/article/KB-000038897?language=en_US
> Know the cause of hardware appliance going in failsafe mode: https://support.sophos.com/support/s/article/KB-000036375?language=en_US

Also log a support case, if it requires any further investigation.