Sorry for the late response. Welcome to the community!
We see you have problems while choosing date range to display stats. This normally does not occur. Can you provide us the login credentials to your website so that we can take a better look at the problem. Currently, we have no reported bugs or issues regarding the same.
I had a look at the plugin on your site. It seems the calendar dates are broken. Normally, there’s a drop-down calendar to select start and end date. I suspect this may happen because some other plugin might be in conflict with Optin Fire. You can try the following steps to troubleshoot:
1) Try deactivating other plugins one by one and check which one causes the problem. If this does not work
2) a) Go to Optin Fire – Import/ Export settings and export all your data (directions are provided there)