So, according to the installation log, you are trying to install NBU Master server, right?
Any reason why you uninstalled 7.6 and not performed an upgrade?
We see errors much earlier in the installation log:
12-27-2018,12:03:57 : Action 12:03:57: Deferred_ConfigureATforNBCert. Configuring NetBackup Authentication for nbwebsvc user
12-27-2018,12:03:57 : Entering ConfigureATforNBCert custom action, deferred phase.
12-27-2018,12:03:57 : Running command: "C:\Program Files\Veritas\NetBackup\bin\admincmd\\nbcertconfig.exe" -u -i.
12-27-2018,12:03:57 : Waiting for command: nbcertconfig.exe
12-27-2018,12:03:59 : Reading pipe broken.
12-27-2018,12:03:59 : The process terminated.
12-27-2018,12:03:59 : Command produced the following output (will display up to 8192 characters):
12-27-2018,12:03:59 : -------------------------------------------------------------------------->
12-27-2018,12:03:59 : NetBackup AT service configuration for web service user failed.
12-27-2018,12:03:59 : --------------------------------------------------------------------------<
12-27-2018,12:03:59 : Command returned status 31.
+ 12-27-2018,12:03:59 : Failed to initialize the AT service for certificate deployment. You must separately run the following command to resolve the issue: "C:\Program Files\Veritas\NetBackup\bin\admincmd\\nbcertconfig.exe" -u
12-27-2018,12:03:59 : Running command: "C:\Program Files\Veritas\NetBackup\bin\admincmd\\nbcertconfig.exe" -m.
12-27-2018,12:03:59 : Waiting for command: nbcertconfig.exe
12-27-2018,12:04:00 : Reading pipe broken.
12-27-2018,12:04:00 : The process terminated.
12-27-2018,12:04:00 : Command produced the following output (will display up to 8192 characters):
12-27-2018,12:04:00 : -------------------------------------------------------------------------->
12-27-2018,12:04:00 : NetBackup AT service configuration for web services failed.
12-27-2018,12:04:00 : --------------------------------------------------------------------------<
12-27-2018,12:04:00 : Command returned status 31.
+ 12-27-2018,12:04:00 : Failed to initialize the AT service for certificate deployment. You must separately run the following command to resolve the issue: "C:\Program Files\Veritas\NetBackup\bin\admincmd\\nbcertconfig.exe" -m
12-27-2018,12:04:00 : Running command: "C:\Program Files\Veritas\NetBackup\bin\admincmd\\nbcertconfig.exe" -t.
12-27-2018,12:04:00 : Waiting for command: nbcertconfig.exe
12-27-2018,12:04:00 : Reading pipe broken.
12-27-2018,12:04:00 : The process terminated.
12-27-2018,12:04:00 : Command produced the following output (will display up to 8192 characters):
12-27-2018,12:04:00 : -------------------------------------------------------------------------->
12-27-2018,12:04:00 : Failed to generate security certificate for tomcat.
12-27-2018,12:04:00 : --------------------------------------------------------------------------<
12-27-2018,12:04:00 : Command returned status 31.
+ 12-27-2018,12:04:00 : Failed to generate security certificate for tomcat. You must separately run the following command to resolve the issue: "C:\Program Files\Veritas\NetBackup\bin\admincmd\\nbcertconfig.exe" -t
It seems that this master is not part of AD domain with no DNS lookup configured. I saw this in the log:
DNS Lookup failed for host bkpsrv error:No DNS servers configured for local system. !
It is therefore important that ...etc\hosts entries exist to correctly resolve local server and client name lookup.
It seems that machine name is upper case and NBU Client name is lower case:
Computer name: BKPSRV
Client_Name (from registry): bkpsrv
Have a look at these 2 TNs:
https://www.veritas.com/support/en_US/article.000125564
https://www.veritas.com/support/en_US/article.100041396
Hope this helps...