If you can share exactly where you are being asked for the key (screenshot description or installation method), I can give a more specific answer.
A green notification should confirm the key is valid and linked. Documentation GLPI 11 4. Key Distinctions glpi registration key
: Required to download and manage plugins within GLPI version 9.5 and above. If you can share exactly where you are
Integrates your instance with official Tier 3 support and bug correction services for professional environments. it has limitations:
While the registration key provides basic security, it has limitations: