No personnel number found for ID number &1 and employer tax no. &3 on &2

What causes this issue?

No personnel number could be found for the transferred data of ID
number, employer tax number, and key date.
The ID number (identification number in accordance with ?139b of the
German Fiscal Code) is stored in the <LS>Fiscal Data D</> infotype
(0012); the employer tax number of the company office for employment tax
is stored in the table <LS>T5D0P</>. The company office for employment
tax is summarized based on the Reporting personnel area using the
subapplication <LS>LSTB</> (Employment Tax Statement).

How to fix this error?

Use the ID number to determine the possible infotype records of the
<LS>Fiscal Data D</> infotype (0012) and check the attributes for the
ELStAM procedure in these records.
Check whether the employer tax number has changed.
After the data has been corrected, use the report
<DS:RE.RPCE2ZD0>ELStAM: Manage Data Records</> (RPCE2ZD0) to make the
assignment. To do so, select the relevant row with the status <LS>Not
Assigned</> and choose <PF>Assignment</>. You can then use the report
<DS:RE.RPCE2VD0_IN>ELStAM Procedure: Update Master Data Using ELStAM
Procedure</> to continue processing the data.

Error message extract from SAP system. Copyright SAP SE.