Using the default shared hosting configuration or default server configuration, when you are demo data it may take more then allowed time.
Fatal error: Maximum execution time of 60 seconds exceeded in ....
So the fix for this is to increase the execution time limit
easy right ?
But what if you are not a developer, how can we make this easier for the clients ?
One quick fix i can think of is to split the demo data into multiple demo (in case you have custom posts)