ORA - 04061 : existing state of has been invalidated
ORA - 04065: not xecute,altred or dropped package body
The above errors may occur in WF when we modify or execute any pLSQL WF Package.
Technically when you apply some PLSQL changes to the database that could impact the mailer/notification code, you should shutdown the agent listener service, apply the changes and re-start them. Compiling a PLSQL package in the Database invalidates the state of that package in other active sessions and the next time the other session accesses that package, it appears invalid though in real-time the package is valid.
To release the issue clear the cache and bounce the WF Listener, WF mailer and Agent Listener.