As mentioned I’d first like to know whether this is possible to begin with.
Subscribers had previously signed up for automatic renewals of their subscriptions and became manual renewals as they were manually imported into the new WordPress installation.
Could someone please shed some light and advise how this is done.
Much appreciated.
Provided you are using the standard Subscriptions plugin, as far as I know the renewals are handled by the subscription plugin, and the processor only handles actual payment requests so your solution lies within the subscription plugin settings.
In particular, each order contains a subscription product. And each subscription product has settings which control whether it will automatically renew or will require manual renewal. Check your product settings – specifically the “for” setting – it’s barely visible in this image provided by WooCommerce
Your problem is that since you’re talking about existing orders, I’m pretty sure the orders’ terms won’t change after you update the products.
What you can do is manually remove the product from each order, refresh the page to get the product adding interface, then add the modified product and the order becomes auto-renewal.
Alternatively, you could figure out how to solve this before inserting the orders so you won’t have to do it manually.