Currently, when importing workstreams between environments, the voice channel needs to be deleted, and re-created in the target system, according to the documentation here: https://learn.microsoft.com/en-us/dynamics365/customer-service/implement/copy-environment-with-omnichannel

It would be great if the migration would work seamlessly so that deleting and recreating the voice channel is not needed after migration. We use the CMT for the migration, and sometimes we get a bug where, after the migration the voice workstream will show two voice channels, even though the source environment only has one voice channel per voice workstream. This forces us to always delete the related voice channels and recreate them in the target environment.

Or, at least, it could be added in the documentation that this step is needed, here: https://learn.microsoft.com/en-us/dynamics365/customer-service/administer/migrate-config-data-for-voice-channel