A customer cannot transfer an existing domain in PBA Control Panel due to the error message 'Domain [domain_name] can not be transfered.' like on the screenshot below:
Provider checked and found that Service Plan for corresponding domain zone exists in PBA, domain zone is present in PBA Domain Manager, the proper registrar and availability checker are configured for it.
However, the required domain zone (TLD) is not present in the list of domain zones available for domain transfer in the error message displayed in PBA Control Panel.
Include Service Plan for the required domain zone(s) into a Sales Category which has the 'Show in Customer Control Panel' parameter enabled.
Usually, Provider creates separate Sales Category for all domain registration plans and all such plans have to be included into this category (it is also configured to be used in the Online Store).
Domain Service Plan for the required TLD (domain zone) is absent in the Sales Category which is configured to be shown in Customer Control Panel.