Can't upgrade to Appointments+

I want to add the Paddings add-on, but there is a hyperlink beneath the add-on saying 'upgrade to Appointments+'. I click this link, and I'm taken to the installation page at WPMUDEV. I click install, and a pop-up appears telling me that Appointments+ is already installed on my site. What's going on? Please can you help?

    Predrag Dubajic

    Hey Richard,

    There's currently an issue with Appointment Lite that cleans up the leftovers when the plugin is disabled via WP dashboard.
    We are looking at fixing this in next release but in the meantime we can install the Pro version manually for you in order to keep the data.
    In order to do that we would need either a FTP or cPanel access to your site.

    You can send us your details using our contact form https://premium.wpmudev.org/contact/#i-have-a-different-question and the template below:

    Subject: "Attn: Predrag Dubajic"
    - Site login url
    - WordPress admin username
    - WordPress admin password
    - FTP credentials (host/username/password)
    - cPanel credentials (host/username/password)
    - Link back to this thread for reference
    - Any other relevant urls

    Note: Please make sure to have backup of your site ready just so we stay on the safe side.

    Best regards,
    Predrag