After a clone is completed, MID server credentials are no longer working on the target instance.
All Supported Releases
This is usually caused by preserving the sys_user table without excluding it as well. For MID server authentication, a local sys_user record with the 'mid_server' role is used. When you configure a data preserver, it will apply the preserved data on top of the cloned data. Without also excluding the data also, the MID server user will be cloned down from prod, and then the preserved MID server user will be applied right on top of it. Since there is a unique index on the user_name field on the sys_user_table, this insert will be blocked.
It is not recommended to preserve or exclude the sys_user table for any reason. If some users must be preserved between instances, it is recommended to export them to XML. The user_name value must also be unique, since you cannot have more than one sys_user record with the same user_name value.