Good evening, @robertrackl. 

Thanks for reaching out to the Community. 

To clarify, are those customers who you're not able to provide statements to, using sales receipts for the selected time period? If so, statements will not generate for those customers because sales receipts don't hit the Accounts Receivable account. Statements are an Accounts Receivable document. You can create a statement by generating an invoice in the same time period as the statement. I've included the steps below to create a statement. 

Please note: The statement window will tell you why your customers are missing. 

1.  From the Sales menu, select Customers. 

2. Choose the customers you need to create a statement for by checking off the customer's names. 

3. Click on Batch actions and hit Create Statements. 

4. In the Statement Type window, pick what type of statement you'd like to make. 

5. Fill in the date fields and select Apply. 

6. Click Save, Save and close, Save and send, or Print or Preview. 

That's all there is to it. Check out, Create and view customer statements for more details. 

Let me know if you have further questions or concerns. The Community is always here to lend a helping hand. Take care and enjoy your week!