Install-CsDatabase : Command execution failed: The network path was not found.
Step 1: From SQL management studio, verify which SQL Server is the primary one for the availability group and note it.
Step 2: In the SFB topology builder, expand Shared Components, right-click SQL Server Stores, right-click the SQL always on availability group used by the pool that you want to update, and then edit properties, change the "SQL Server FQDN:" from the <listener FQDN> to the <SQL Server FQDN> which is currently primary as per step 1.
Step 3: Publish the topology.
Step 4: Run the Invoke-CsManagementStoreRepliction cmdlet to replicate CMS.
Step 5: Verify that CMS replication is complete by using the Get-CsManagementStoreReplicationStatus cmdlet.
Step 6: Run the install-csdatabase -update -ConfiguredDatabases -SqlServerFqdn <listener FQDN> -Verbose PowerShell command.
- Listener FQDN is still used in the cmdlet.
If topology is being upgraded from Skype for Business Server 2015 Cumulative Update 7 (July 2018 Cumulative Update) to Cumulative Update 8 (January 2019 Cumulative Update), you can skip applying the changes that are made to the SQL Server databases. Therefore, you don't have to run the Install-CsDatabase cmdlet for this particular scenario.
After the database is updated, follow step 2 and change the "SQL Server FQDN:" from the <SQL Server FQDN> to the <listener FQDN>. Then, publish the topology and start the CMS replication as per step 4.
This issue will be fixed in a future cumulative update.