No-status when discount applied on recurring plans

We have a problem with a discount code we're running on our recurring (SONATA) plans. The discount (sonata18) is $4 off the first invoice. Everything works fine except the plan never goes into "Active" status and remains "No-status" This was working fine just about 3 days ago. I've been manually changing them to active as they come in.

If the discount code is not applied, the plan goes into "Active" status immediately. We also have fixed plans on our website with discounts, and no problems with those whatsoever.

I was trying some different settings in the Payplans-Quick-Registration app which may have triggered this. I've tried changing the settings back but the problem persists.

Thanks for your help!