The system will not allow you to create an ILR for a user, if the User details tab of the ILR has not been saved. Normally, the ILR is either created during Onboarding by the user or by the Admin by first saving the User part/tab.
If you are unable to save the ILR by clicking on the Create ILR link in User Profile, then click the User tab in the ILR, and then click Save. This will create an ILR for this learner by saving all the user and Aims details.