WP Slider

You should consider posting this in plugins. Include the link to the plugin, the Author might help you. In my experience when something like that stops working, it means a Javascript module did not load on install, or is corrupted.

I am new here, thanks for pointing this out to me. I thought this is not a plugin and comes with WP as it says WP Slider – I do also not see a plugin called WP Slider.

It may have come with your theme

https://www.ads-software.com/plugins/simple-slider-ssp/

Thanks, will check.