In order to persist the license key, it must be stored on disk so that the value can be read on the start of your application server.
FusionReactor will attempt to persist the license key to either {FusionReactor Directory}/license/license.key or {FusionReactor Directory}/instance/{Instance Name}/conf/reactor.conf.
When you see "Cannot persist license key XXXXX-XXXXX-XXXXX-XXXXX-XXXXX" This indicates there is some form of permisions issue saving the license key to disk.
To resolve this you can do one of the following:
1. Ensure the user running your application server has read and write Access to your FusionReactor Directory
2. Ensure than your Anti-virus software is not blocking the java process of your application server from writing to disk
You can also set the system property -Dfrlicense=XXXXX-XXXXX-XXXXX-XXXXX-XXXX in you JVM args, at which point the license key will not need to be persisted to the disk at all.