eBook sales

Yes you can, as long as you meet the criteria on the banned and restricted items list in the help pages.

https://help.trademe.co.nz/hc/en-us/articles/360010959212-Banned-and-restricted

I am the sole copyright owner; I author the book but use a pen name (author name). Am I still allowed to list it if the name is different to my account name?

Sounds like you meet the criteria Deziree, but it's always best in these cases and where IP rights are involved to let Trademe know. I'm sure you will have some documentation you can send to Trademe. They will make a note on your membership of your IP rights in case anyone queries listings. They have a form that can be filled in and include attachments for this purpose on this page below. Be proactive and rest easy.

Proof of intellectual property – Help - Trade Me