In the contract module, when trying to create an invoice for a contract/customer of mine, using "Operation Create Invoice", I get the following message: "No invoice was created, either nothing can be invoiced or you are not allowed to create a contract invoices".

If I run the Report "Invoice-able Contracts" for the same customer, nothing is printed in the report. Also, the Maintenance Routine "Create Invoices" does not create an invoice for this customer

I've always had the relevant Access Rights to generate these - any idea why I am now unable to do so?