EHP key &1 is not permitted

What causes this issue?

To create an assignment to the selected structure, you cannot use EHP
key &V1&. This may be caused by:
You have selected the wrong EHP key.
The entries in tables IWB_EHP_F4, IWB_EHP_SWC and IWB_EHP_CONTEXTH are
incorrect.

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?

Use the input help for the EHP key.
If you cannot find the right EHP key, contact your power user for
Knowledge Warehouse (KW).

Procedure for System Administrators

Check the entries in all tables and correct the definition of the EHP
key.
Context parameters in table IWB_EHP_CONTEXTH
Software component (SWC_NAME) and software component release
(SWC_RELEASE) in table IWB_EHP_SWC
Value in table IWB_EHP_F4 (definition of enhancement packages and
support packages in accordance with PPMS)

Error message extract from SAP system. Copyright SAP SE.