Subscription keys are time-bound. If your subscription lapses, the key will become invalid, and access to the Network Catalog will be restricted. Open Source vs. Subscription
Ensure your GLPI version is up to date. Older versions may use outdated authentication protocols that are no longer supported. glpi registration key
If your GLPI registration key is not working, consider the following common hurdles: Subscription keys are time-bound
Go to the "Setup" menu and select "General." the key will become invalid