Storyline: Button on a pop2

Calling it a popup may confuse developers since it's more literally just a layer. If your layer is closing when you don't want it to, its properties likely need to be changed. The cog in the bottom-right of the screenshot you shared will show the properties of your currently selected layer. It sounds as though this slide's layer properties are hiding it when you don't want it to.

I confess I don't understand why the layer's timeline is being used to change images. Is the expectation that learners will have read the entire image before being forced to the next image? Best practice is to let users control the flow of material they're expected to read. Can I recommend some simple triggers to change the states of images to Hidden and Default? One image can begin the layer Hidden and the other image visible, and then when someone clicks a button, the Hidden one is made visible and the visible one is made Hidden.