Hello,
Sorry to hear you are having trouble.
looks like a bug in the authenitcation component os start11
Very unlikely. While we have seen what you are describing in the past, almost without exception, it is something external that the end user is not aware of. Having them agree that this is the possibility is nearly as difficult as finding out what that is.
I like the many new features offered that you can not even find some of these in Windows 10 but the having to activate something that I OWN 6 licenses for every week is stupidity.
Under the account you are posting under, you have no Start11 licenses. I would need to know under what account you do, cowen.
I have a start8 activation code but I can no longer get the software for start8 as i can not find it online at a legitimate site.
That said, Start8 is under the account you are posting under. It is, and always have been, available under your account. Either of these links will help you obtain it:
https://store.stardock.com/myaccount/products
http://www.stardock.com/support/productkeyretrieval
That said, if you are on Windows 10 or greater, Start8 will not work on it.
If activation files are being removed there are two reasons. Firstly a machine is being deactivated due to user action or too many activations of a key (installed on say 6 machines with 5 licences). Secondly a tool to 'cleanup unused files' is deleting the files. This is the most likely reason.
Neil is correct here. Users are sometimes using the same key to activate many PCs. A license has exceeded its activation limit and the user, via an activate prompt telling them so, is deactivating everything else to activate on the PC they are on. Its a matter of time before one of the other PCs that was last silently trying to reactivate starts to complain that it cant.
Looked like the software reinstalled itself upon a reboot.
There is no mechanism in the app or the installer that would do this, cowen. However, if this is being used in an 'EMS' environment - where IT admins police the software that is on any PC they manage - there are many apps \ policies they would use to restrict what software is on them. It would be most prudent to reach out to them to see if they could provide some inside there.
If this is not managed by IT staff, if you own any Maleware products or 3rd party Antivirus software, please check their logs to see if either of them is removing the activation file.
If you do not find anything, I need to know the account you have your license under. You can PM me the email address like in this example:

Sean Drohan
Stardock Product Lifecycle Manager