Enabling Time in Feature Layers

[AndySkelton]

I have a couple of feature layers published to my federated hosting server for my Portal. I've enabled time on them when I published them, and their respective rest endpoints all have a time info section:

But, when I go to enable time on the layer's overview page, there's no option to do so:

I need to be able to use that time field for analysis on a webmap for a client, but something's eluding me here... interestingly enough, I have another feature layer that has no option to enable time on its overview page, but does have it enabled anyway, and I can enable/disable the time slider on webmaps with it. I know it's possible, but I can't seem to remember how I did it with that one layer.

Any ideas?