Definitely a JS error in the admin. One of your other plugins or current theme must be embedding a buggy code into Responsive Lightbox settings page.
I had same problem too.
I use TheCartPress plugin. One of the option in the plugin causes this issue. I disabled “Load Bootstrap JavaScript” (TheCartPress), problem solved.
Same is happening to me, but I can’t find the plugin that is causing the problem. All plugins seem to be working ok, but I can’t save options on yours.
I believe this issue happens because of some incompatibility between plugins. To find which plugin that incompatible with “Responsive Lightbox”, you first should try to disable all other plugins. If this won’t solve the problem, you might need to change to the default theme (sometimes, theme can cause problem too).
If disabling the plugins can solve the issue (temporary), then you enable all the plugins one-by-one to see which one is causing the problem.
As I said, it only solves the issue temporary. To really fix the issue you need to contact the plugin’s developer or ask dFactory to make it compatible with the plugin.
Hope it helps.
