Is this Autopilot with Azure AD Join? Or Hybrid Azure AD Join? Autopilot with Hybrid Azure AD Join does not support %serial% for the computer name. If it is Hybrid, it creates two device objects. You might be looking at the other device object that needs to sync still.
Were there any errors during the Enrollment Status Page? You can use this guide for troubleshooting - https://oofhours.com/2019/10/08/troubleshooting-windows-autopilot-a-reference/