To upgrade WP Simple Pay Pro from version 2.5 to 3, you’ll probably want to remove version 2.5 first.
Some site owners may want to run both plugins side by side on the same site if they need extra time to migrate. But if you don’t need to do this, it’s simpler to remove version 2.5 before installing version 3.
Due to massive changes to the settings and structure between the two releases, there is not a way to migrate your settings or shortcodes from version 2.5 to 3.
In addition, we ended support for version 2.5 on [v2-end-of-life-date-only], exactly one year after version 3 was released.
To continue upgrading to version 3, first log in to your WordPress admin and click on Plugins → Installed Plugins.
Find WP Simple Pay Pro 2, then click Deactivate. Repeat this for the Subscriptions Add-on if it’s active as well, or use the “Bulk Action” drop-down if you prefer.
Now scroll back down and click Delete on the deactivated plugins one at a time (or again use the “Bulk Action”. Finally, you’ll be prompted to confirm the version 2.5 plugin deletions.
Now you’re all set to install WP Simple Pay Pro 3!