1. Check if you have at least 10GB free space
2. Stop ATA and expand disk to get 10 GB free
3. Take checkpoint
4. Run ATA_1.6_Update
5. Accept and it will update .NET to 4.6.1 and ask to reboot, go for it.
6. After reboot update will continue.
7. At the end update will propose to launch ATA https://url/configuration
8. Download gateway package, copy ZIP to all gateways
9. Run setup and it will update .NET first
10. As in case of main server after restart setup will continue and will update gateway.