appmanager's problem

hello
my appmanager is free evaluation, but one day I reboot my server it appears a message that told me to enter license file. otherwise I can't use appmanager. What should I do to avoid this situtation?

""Licensee Details

Please enter the license file that you have obtained from AdventNet. It
can either be an Evaluation user license file or a Registered user
license file. ""

thanks