Banner Manager - I can't activate/deactivate banners

I have an odd situation - I have four banners running on my home page, and they work just fine. I wanted to add a new one, and did exactly what I've done for the others - new banner, added to the same group with the same settings. Only it doesn't display. What's more, when I deactivated another banner from the same group, the setting didn't "take", and the banner is still showing up.

Is this a common problem, or am I just lucky?:unsure:

Any help much appreciated!

Are these banners images, or HTML content?

Images.

Cache cleared before reloading page(s)? Do you have such content set to be cached by servers and thus not yet seeing the change(s)? Tried a different browser, or a different device to try to see the change(s)?