In table &, FELDS/FELDM missing for &

What causes this issue?

An internal error has occurred during the availability check.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

INCLUDE NA_NIX_MEHR
INCLUDE NA_SYSADMIN1

Error message extract from SAP system. Copyright SAP SE.