Interinize

In this case I believe you have to manually generate the invoice and update the next due date under the customers service for this billing period. Updating the next due date will ensure the system will automatically invoice the customer as normally for the next billing period.

In the Client Profile screen, on the summery tab under Invoices/Billing you should see a "Generate Due Invoices" link. Does this work? Edit: When you changed the billing cycle, you should have ticketed the "Auto recalculate on save" check box next to the Recurring Amount. If you didn't check this, you may have to manually change the recurring amount and then generate due invoices. I should probably note that I've never done this before so the information I'm providing may be slightly inaccurate.

I believe this may be just an oversight by the WHMCS dev team. Going into Billable items by Billing => Billable Items => Add New and the box allowing you to enter the number of times is certainly missing. However if you go into a Client Profile => Billable Items (Tab) => Add Billable Item, it does allow you to enter the number of times you'd like the billable item to recur. Perhaps use this as a work around in the mean time?

To bill someone $50.00 once a month for 3 months using billable items, you would use the following configuration in WHMCS. ~ Recur Every 1 Months for 3 times. ~ This is essentially telling WHMCS to bill the client once every month for 3 months. Hope that helps!

Perhaps it's worth posting how you resolved the issue just in case other users experience the same problem you did?