Navigation to characteristic value maintenance is not possible

What causes this issue?

To edit characteristic values, the following prerequisites have to be
met:
The data type (<LS>Basic Data</>) has to have format <LS>Character
Format</>.
The maximum number of places (<LS>Basic Data</>) is 18.
Function module WRF_CHECK_CHAR_VAL must be specified in group frame
<LS>Value Check via Function Module</> in the <LS>Values</> tab page.
You have to save the characteristic after you create or change it.

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?

Check whether the described prerequisites are met. If necessary, change
the data and save the characteristic before you start processing the
characteristic values again.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.