Unable to generate selection screen: Program "&" not generated

What causes this issue?

When making a background job request, you specified a user name which
does not have a valid user type.

System Response

The system outputs an error message and you must correct your input.

How to fix this error?

Please check the user type. The following values are permitted for
background processing:

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

Dialog user
Background user
Batch input user
You may also need to correct the spelling of the user name.
If there are no spelling mistakes and the user name is a different type
from those mentioned above, but is still intended for the authorization
check in a background job, you must modify the user type accordingly.
To do this, contact your system administrator.

Error message extract from SAP system. Copyright SAP SE.