WooCommerce Subscriptions blank settings after upgrade

If you have a blank WooCommerce Subscriptions or WooCommerce Checkout settings page after upgrading to WordPress 4.4 while running WooCommerce Subscriptions, then you might have run into an error caused by a modification in a core file that was released with WordPress version 4.4. This issue also prevents anyone from adding subscription products to the cart.

Turning on WP-DEBUG  will get you this kind of error:
Fatal error: Uncaught exception ‘Exception’ with message ‘SSL certificate problem: unable to get local issuer certificate’
The error has been fixed already and will be released in WordPress version 4.4.1.

WooCommerce database transient issue

We have an ongoing discussion here.

https://wordpress.org/support/topic/too-many-wc-transients-created-in-db?replies=40

If you read a bit then you see that my splendid mate Mike Jolley is aware of the problem and has implemented a possible solution for this in WooCommerce 2.5 – fingers crossed

But you do not need to wait that long.
You can try and tackle this manually using this:

plugin: https://wordpress.org/plugins/delete-expired-transients/
plugin: https://wordpress.org/plugins/transients-manager/
plugin: https://wordpress.org/plugins/artiss-transient-cleaner/
Using our tools will also alleviate the issue.