Tomcat gets update from 8 to 9 from SP3 to SP4 - with this upgrade java is NOT upgraded to support tomcat 9. Make sure you upgrade java to 1.8. If not tomcat may not even start.

I also had to update the context.xml in the manager apps to allow my IP address for the login prompt to reappear, otherwise you just get the access denied page.

I'm not sure if this is related but catalina.out is not being created or updated. Has anyone else run into any other troubles ?