Avamar: Failed to Update or Connect to a Data Domain System due to Locked DD Boost User

All backups from Avamar to Data Domain fail with: 

2020-02-09 10:05:39 avtar Error <10542>: Data Domain server "datadomain.local" open failed DDR result code: 5075, desc: the user has insufficient access rights (Log #1)
2020-02-09 10:05:39 avtar Error <10509>: Problem logging into the DDR server:'', only GSAN communication was enabled. (Log #1)
2020-02-09 10:05:39 avtar FATAL <17964>: Backup is incomplete because file "/ddr_files.xml" is missing (Log #1)
2020-02-09 10:05:39 avtar FATAL <8941>: Fatal server connection problem, aborting initialization. Verify correct server address and login credentials. (Log #1)

All Maintenance jobs fail with: 

 MSG_ERR_DDR_ERROR

The below command reports the checkpoints as invalid, and the error:  

admin@avamar :~/>: cplist --full

cplist: ERROR: ddrmaint: <4750>Datadomain get checkpoint list operation failed.
2020/02/09-12:08:56.31504 [cplist]  ERROR: <0001> ddrmaint: <4750>Datadomain get checkpoint list operation failed.
cp.20200122200414 Thu Jan 23 00:04:14 2020 invalid --- ---  nodes   1/1 stripes   1875
cp.20200122201338 Thu Jan 23 00:13:38 2020 invalid --- ---  nodes   1/1 stripes   1875
cp.20200123043629 Thu Jan 23 08:36:29 2020 invalid --- ---  nodes   1/1 stripes   1876

The command below reports the same error: 

admin@avamar:~/>: ddrmaint cplist

<4750> Datadomain get checkpoint list operation failed.

The "DDR Authentication flag" is disabled in mcserver.xml: 

root@avamar:~/#: grep -i "use_ddr_auth_token" 

/usr/local/avamar/var/mc/server_data/prefs/mcserver.xml
              <entry key="use_ddr_auth_token" value="false" />

Due to several and frequent attempts from Avamar with an incorrect DD Boost password, the account gets locked, closing all the connections to the Avamar.

Attempting an SSH connection to the Data Domain as the DD Boost user shows that the account is locked due to X failed logins: 

admin@avamar:~/>: ssh ddboost@datadomain

EMC Data Domain Virtual Edition
Account locked due to X failed logins
Password:

From a Data Domain account, the output of the below command shows the DD Boost user as enabled: 

sysadmin@ddve# user show list

User list from node "localhost".
Name       Uid   Role    Last Login From   Last Login Time           Status   Disable Date
--------   ---   -----   ---------------   ------------------------  -------- -----------
sysadmin   100   admin   xx.xxx.xx.x       Mon Feb 10 11:57:06 2020  enabled     never
ddboost    500   admin   xx.xxx.xx.x       Mon Feb 10 12:07:07 2020  enabled     never
--------   ---   -----   ---------------   ------------------------   -------------------
2 users found.

The ddfs.info file is showing authentication failures from the Avamar IP Address.

Contact Dell Support to work with the Avamar and Data Domain Support teams to apply the resolution.

This resolution must be followed on each Avamar using the same DD Boost user: 

ddboost@ddve# ddboost storage-unit show

Name                Pre-Comp (GiB)   Status   User      Report Physical
                                                           Size (MiB)
-----------------   --------------   ------   -------   ---------------
avamar-xxx          515401.8            RW       ddboost                 -
-----------------   --------------   ------   -------   ---------------
 D    : Deleted
 Q    : Quota Defined
 RO   : Read Only
 RW   : Read Write
 RD   : Replication Destination