Hi Anindya Das,
We have reached out to the content author and got the confirmation that the Next Page button issue is being addressed.
In the meantime, you can navigate to the Start page, select the required units, and complete them individually. Additionally, please note that the Interactive Lab Simulation has been removed.
We appreciate your patience and understanding.
If the information is helpful, please Accept Answer & Upvote so that it would be helpful to other community members.