When the hp payment plugin is enabled, it forces all unpaid listings to be unpublished. Here are the steps to create one/more subscriptions for your existing listings.
- Create a plan for, say 100 listings in backend. Keep it unpublished so others cannot subscribe it.
- Create a subscription for administrator to that plan (because admin will be the owner of existing listings). Apply/Save subscription. After saving edit that subcription record again and click the Allocate listings button. Select your hp listings from drop downs and click save again.
- If you have more than hundred existing listings, you may need to create more than one subscriptions like the one you created in above step.
- Publish your listings.