The slider is an interaction in a module where you must click and drag the icon (commonly shown as a <> symbol) along the line to "slide" through the content.
Known issues with this interaction include out of date browsers, laptop scaling, and potentially having some interactions blocked in the settings by your IT/System Administrator.
If discussing this issue with your local IT/Systems administrator don't solve this issue, potential solutions include:
If you are using a laptop, the browser may be "scaled", meaning it is automatically resized to fit the window. Adjusting the Zoom level (this can be done by holding the CTRL key and pressing + or -) may help to fix the issue.
Alternately, using a different browser, such as Internet Explorer, Edge, or Firefox may allow you to access and complete the training that is assigned to you.
In some cases where this does not solve the issue, please try accessing your account via a different device.