If external integration was added to Linnworks and then deleted it will not be possible to add it again due to this error message:
“UnprocessableEntity” - Please use a unique account name.
There are two solutions:
1. Re-integrate the channel with a different name.
Please Note! Before integration please make sure that all of the unnecessary orders are shipped because otherwise duplicate orders might be downloaded. Linnworks check for duplicates based on Source, Subsource and Reference Number. If you change one of them - SubSource in this case - old orders may be downloaded to the system.
2. Integration developers would be able to remove the account from their records. That should allow to re-add the channel with the same name.