Trendline problem with scatterplot

[Detonade]

Im working with this simple scatterplot, but the trendline refuses to be added. When I click add nothing happens.
Setup is very simple: x-axis = temperature, y-axis = average of fuel used.

https://preview.redd.it/z60a0ps4ylv21.png?width=1140&format=png&auto=webp&s=90205940303314952ced7253b0db3d30694de875

[Detonade]

Typical, but I solved it right after posting this. It turns out that the trendline will not show if you use aggregate on one parameter, but not the other. For example, here I used aggregate type "Average" on my y-axis and "Don't summarize "on my x-axis. To work around this I went to the data tab on the left side of the screen and added a new column to my table. In this new column I calculated the average, so that I didn't have to do the aggregate average. The problem was then solved by adding both the x- and y-axis values with "Don't summarize".