Code 5 means the plugin has been activated more than 3 times, and all available activations have been used.
To avoid this in the future, please open your plugin and go to Menu > License Info > Deactivate before uninstalling or moving to another computer.
After that, if your plugin is still asking for an offline activation file:
- Open the plugin and click Open Folder
- Delete the offline activation XML file
- Close & open the plugin and enter your license key again
The message should disappear, and your plugin will activate normally.