The error can be seen in a pop-up window in the Vault Administration Console after attempting to clear the index locations from backup mode:

In the event logs the following can be seen on multiple processes such as StorageArchive, StorageDelete, Admin Console, etc.
Log Name: Veritas Enterprise Vault
Source: Enterprise Vault
Date: 03/31/2021 4:02:08 AM
Event ID: 7344
Task Category: Storage Archive
Level: Error
Keywords: Classic
User: N/A
Computer: EVSERVER_03.EV.LOCAL
Description:
Could not contact the Indexing Service
Please check the Indexing Service has been started on [SiteName]
Internal reference:
CCIAO/cc : Error loading type library/DLL. (0x80029c4a)
Log Name: Veritas Enterprise Vault
Source: Enterprise Vault
Event ID: 7344
Task Category: Storage Delete
Level: Error
Keywords: Classic
User: N/A
Description:
Could not contact the Indexing Service
Please check the Indexing Service has been started on [SiteName]
Internal reference:
CCIAO/cc : Error loading type library/DLL. (0x80029c4a)
V-437-7344
The cause of this issue is currently under investigation. It appears that when EV is uninstalled, some references to the component EVSharedManagedInterfaces.tlb remain in the registry. If EV is reinstalled to a different installation path, this issue may occur.
Workaround:
Warning: Incorrect use of the Windows registry editor may prevent the operating system from functioning properly. Great care should be taken when making changes to a Windows registry. Registry modifications should only be carried-out by persons experienced in the use of the registry editor application. It is recommended that a complete backup of the registry and workstation be made prior to making any registry changes.
Update the win64 and HELPDIR registry keys under the following registry path to have the correct drive letter for the EV installation directory. (NOTE: There are several c.X folders so it's necessary to update it for each registry key.)
[HKEY_CLASSES_ROOT\TypeLib\{535D6634-CA6C-4C9D-94C6-6C6EA5F88D63}\c.4\0\win64]
DWORD: Default
VALUE: C:\Program Files (x86)\Enterprise Vault\EVSharedManagedInterfaces.tlb
[HKEY_CLASSES_ROOT\TypeLib\{535D6634-CA6C-4C9D-94C6-6C6EA5F88D63}\c.4\HELPDIR]
DWORD: Default
VALUE: C:\Program Files (x86)\Enterprise Vault\
After updating, restart the EV services.
There are currently no plans to address this issue by way of a patch or hotfix in the current or previous versions of the software at the present time. While this issue may be resolved in a future major revision of the software at a later time, it is not currently scheduled for any release. If you feel this issue has a direct business impact for you and your continued use of the product, please contact your Veritas Sales representative or the Veritas Sales group to discuss these concerns.