BAdI class & does not exist

What causes this issue?

The BAdI class for your BAdI definition does not exist.

System Response

This condition is unacceptable, since Business Add-Ins cannot function
under these conditions.

How to fix this error?

Inform your system administrator.
If this error is due to a transport problem, create the interface in
the transport source system and re-transport it.

Error message extract from SAP system. Copyright SAP SE.