SQL SERVER Agent not starting

SQL Server Agent is not starting after in place upgrade of SQL server from 2012 to 2019

I have done in place upgrade of SQL server from SQL 2012 Standard Edition (64-bit) SP4 to Microsoft SQL Server 2019 (RTM) - 15.0.2000.5 (X64) Sep 24 2019 13:48:23 Copyright (C) 2019 Microsoft Corporation Standard Edition (64-bit) on Windows Server 2019 Datacenter 10.0 (Build 17763: ) (Hypervisor).

But after upgradation, sql server agent is in stopped state.

I have tried with Local system account also but still no luck.

Error in windows event logs is SQLServerAgent could not be started (reason: SQLServerAgent cannot start because the msdb database is read-only).

I have checked and confirm that msdb database is not in read only state.

Can someone help me to resolve this issue.