Assignment to advertisement or unsolicited applic. group mandatory

What causes this issue?

You have not assigned the applicant to an advertisement or an
unsolicited application group. It is essential when first entering an
applicant's data to assign him or her to an advertisement or
unsolicited application group. The assignment enables a selective
evaluation of the applicants to your enterprise.

How to fix this error?

Assign the applicant to either an advertisement or an unsolicited
application group by making the relevant entry in the <LS>Advert</> or
<LS>U.app.gp</> field.

Error message extract from SAP system. Copyright SAP SE.