The server will not shut down, and you will not lose data. The iLO card simply reverts to the functional tier, meaning you lose the ability to use the graphical remote console while the OS is running.
If budget is a concern, consider:
Verify that the status changes to "Licensed" and the license type reflects "iLO Advanced." Frequently Asked Questions (FAQ) Can I use an iLO 5 or iLO 6 key on an iLO 4 system? hp ilo 4 advanced license key free