Unable to Join Replicas to Available Group – Download configuration timeout. Error 47106

Error:

Availability group xxxx is not joined on the secondary replica xxxx. (Microsoft.SqlServer.Management.HadrModel)
 
 Program Location:
 at Microsoft.SqlServer.Management.HadrModel.HadrTask.Perform(IExecutionPolicy policy, CancellationToken token, ScenarioTaskHandler taskDelegate)
    at Microsoft.SqlServer.Management.Hadr.JoinDatabaseToAvailabilityGroupWorkItem.DoWork()
    at Microsoft.SqlServer.Management.TaskForms.SimpleWorkItem.Run()

Failed to join local availability replica to availability group <ag1>. The operation encountered SQL Server error 47106 and has been rolled back. Check the SQL Server error log for more details. When the cause of the error has been resolved, retry the ALTER AVAILABILITY GROUP JOIN command. 

Download configuration timeout.

SQL Server error 47106

Message
Login failed for user ‘Domain\ComputerName$’. Reason: Could not find a login matching the name provided. [CLIENT: ]

Fix:

Use domain account to run services on both primary and secondary replicas.

Sources:

https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/troubleshoot-always-on-availability-groups-configuration-sql-server?view=sql-server-ver15