Is your SAS platform on or above SAS 9.4M3? I see that this syntax is supported only on and above this SAS Version.
Syntax for sas-update-backup-config
The sas-update-backup-config command has the following syntax.
<-sourcetype CONFIGDIRECTORIES | CONTENTSERVER | DATABASE
| CUSTOMDIRECTORIES | METADATASERVER>
Note: This syntax is effective with SAS 9.4M3. In previous SAS 9.4 releases, the syntax includes only the web connection options and the -inputdata option.
I am seeing the documentation on this link and it states that using sas-update-backup-config you can only update a few things as below:
Use sas-update-backup-config to update the backup configuration properties that are in effect for the deployment. You can do the following:
Update your site’s basic backup configuration, including the number of days to retain backups, email addresses for alerts, and whether scheduled backups are to run.
In deployments with homogeneous operating system environments, you can also use this command to specify or update the central vault location.
Define filters that specify tiers, servers, databases, directories, or files to include or exclude from the backup.
For the metadata server, the filter definition can contain an option to reorganize the metadata repositories.
The configuration changes and filters affect all subsequent scheduled and ad hoc backups.
I also tried to change this config path using SAS Backup Manager, However I wasn't able to do that. I think your best bet is to add your existing config directory (which was missed out due to typo) as a custom directory which will then be included into your backup config.
Since you haven't provided any info on what the error was like, if it was failing directly when trying to fetch SASConfig directory or it only skipped the directory/tier and ran successfully for other tiers. Based on which my suggestion may work or not.
I would suggest to reach out TS for more support if you do not wish to try out alternatives. I wasn't able to find much on how to directly update the ConfigPath. Understand it is auto picked by SAS Deployment Manager Agents which help in running the backup process.