Hi @JamesDrew,
A warm welcome to the Bunnings Workshop community, it is fantastic to have you with us.
The first thing you should check is that the battery is fully charged. If not, then charge it fully and try again.
If your powerhead works perfectly fine with other attachments, then logic would say there is an issue with the new line trimmer attachment.
Can you advise the specific model number of the line trimmer and the power head?
I will check the compatibility of the two products to see if this is the cause of the issue.
If there is no compatibility issue, then there could be an issue with the connection between the two. If this is the issue, then it is worth returning to the store of purchase with your receipt. Bring the powerhead and the line trimmer attachment with you so the helpful Power Garden team can troubleshoot the issue with you. If it turns out the issue is with the trimmer attachment, then you are entitled to a replacement.
Let me know if you have any further questions.
Jacob
