When uploading lists/CSV files in Studio using Bulk Import, some successful imports display an "An internal error has occurred" message.
- Studio | People – Import Users
It is expected that the Details column will display more details regarding the status of the import or be blank if all records in the file have been processed and the generated audience is available for use.
This has so far been reported in the Classic Studio user importer, but it is possible this could also impact the new Studio version.
A workaround is not yet understood for the new Studio. Please check the current status of this issue on the Known Issues Tracker. (Issue ID: MAGIC-6487)