And welcome to Tikiwiki community.
Y have no idea myself. But isnce the intratiki messaging is buggy right now for plain regisered users, I answer here to this and related issue.
Dump is an old feature, and it might not have been updated for a while by any coder (not sure, anyway, just guessing).
If you see no attachments, then I would suggest:
- update the Documentation page (whatever it is) to reflect this information
- add a feature request, if you wish, so that it can be kept in mind for some coder in the future when willing to reuse or improve the dump feature:
Ensure you don't have any encoding problems (see Understanding Encoding and the recent fixes in Tiki5rc1, in case you upgraded from a previous tiki branch with non-english content...)