Why do I have 0 in revenue statistics when we have orders?

By default, the module filters orders by invoice date. If your orders have no usable invoice date, they are not included in the selected period.

If your store does not generate invoices, open Global Settings in the module configuration, enable Use order creation date instead of invoice, then save.

Only use the order creation date if the module does not display any data. This setting changes the date used to assign orders to periods; it does not create an invoice.

If revenue is still zero, also check the selected period, store, filters and Status of valid orders. An order must satisfy all these conditions to be included.

See also How to verify that the data provided by the module is correct?

Fictitious example: the option is enabled and saved in this screenshot. Use it only if the module displays no data; the other filters still apply.