Hi Tia,
I apologize for the inconvenience caused by the
Add Trendlines to Multiple Series feature in the current version, which requires optimization. We can guarantee that you can add trendlines using the data format that was sent to you earlier. However, if you prefer to use the data format that you supplied, you can try to modify the Series X value to your data on the x-axis by following these steps:
Rest assured that I've already forwarded the issue to our development team to address in a future release. We appreciate your feedback and thank you for using our product!
Amanda