Hi Paul,
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)
b) re-install the plugin and import your data.
Let me know if your problem gets resolved!
Thanks & regards,
Prajal,
99robots Team