If 'latched' status messages are cleared, they are cleared. In order for them to re-appear the associated fault needs to occur. For engine related faults that usually means an engine run. Even if the valve is deactivated, the EICAS logic will often inhibit setting the message if the engine is not running. That's part of the reason for having 'latched' messages. (BTW, on a 767 you can override the EICAS engine running logic by setting the fuel switch to RUN and leaving it there for at least 5 minutes but you need to use care when doing that - it can also turn on things like probe heat that can quickly overheat - that's why it's a MM procedure with the associated warnings, not something we tell the pilot about).
Not sure about this, but back in the deep recesses of my memory I'm thinking Boeing got rid of the Isolation valve light as part of the post-Lauda sync lock mod...