That usually is caused by installing the demo when Slider Revolution was not installed first. If you’ve not made modifications to the demo yet, you can try installing Slider Revolution from X > Validation and then install the Agency demo again.
If it still doesn’t help, it could be because of hosting resource limitation. This usually is caused by low Max Execution time. Please contact your web host to increase your Max Execution time to 300 seconds. Your server also needs to meet Slider Revolution’s requirements particularly at least a Memory Limit of 256M, Upload Max Filesize of 100M and Max Post Size of 100M. All of which must are surely familiar to your web host and they are capable of increasing it depending on your plan so you need to contact them.

If you have further questions, please open a separate thread because mixing topics in a thread often leads to confusion thus slowing our response times which is not good both for customers and the support staff.
Thanks.