When you create a Full Copy Sandbox, please make sure the "Include Chatter Data" checkbox is checked.
Here are Steps:
1. Go to Setup > Sandbox, and click New Sandbox Button
2. Enter sandbox name and click next button in to "Full" column.
3. Select All and check "Include Chatter Data" Checkbox and click create.
Once sandbox is created, you will get email with instruction on how to access sandbox.
To make sure Simpplr is working properly, you will need to change the Rest_API_URL under "Remote Site Settings".
Go to Salesforce Settup, search for "Remote Site Settings". Click on "Edit" next to Rest_API_URL, and change the instance to match the one of your sandbox.
If you are not sure what to enter, go to Salesforce Set Up > Company Information, you will see an "Instance" field:
In this example, cs97 is the number for sandbox. The Rest_API_URL should be https://cs97.salesforce.com . "CS" should be in lower case.