I have read the terms of your refund but in my case I should have been warned about the fact the email used to buy the plugin through freemius must be able to send mail through the website that the Ivory search pro plus plugin is applied to.
In my case where the Post SMTP plugin and the Office 365 paid extension to the Post SMTP plugin is used, my email address cannot be used to send mail from the website, which is YOUR problem with the way you choose to validate the Pro Plus plugin.
I have not come across the same problem with the other Freemius paid plugins on the same site including WP sheet editor and the Office 365 extension to Post SMTP which use the same email to purchase them.
I have also not come across any difficulty getting a refund from a plugin company where I can’t use their plugin, which is very disappointing as the time I am wasting on this is mounting up.

Refunds
Ivory Search offers refunds on software within 30 days of purchase. Before requesting a refund, please use the Contact Us tab on the Ivory Search settings screen within your WordPress Dashboard to open a support ticket so that we can help you.

Refunds will be offered at our sole discretion and must meet all of the following conditions fully:

You are within the first 30 days of the purchase of the plugin.
You have attempted to resolve your issue(s) with our support team by opening a support ticket through the “Contact Us” in the plugin’s admin settings.
By upgrading, you agree to this refund policy and relinquish any rights to subject it to any questions, judgment or legal actions.

This policy does not cover refunds for the following cases:

Missing feature(s)
3rd part conflict
Discovering a better alternative
Customer changed their mind
Refunds ARE NOT provided for renewals.

Hello Keymaster
No I can’t give you access and I can’t change my authorised email in Freemius without ruining all the other website plugins that I have running under that email address.
I still want this plugin but I can’t activate it.
If I uninstall it and instruct my client to buy it (again) and try to activate it, if they can activate it using their email address, will you give me a refund?
I am uninstalling it now.
Cheers
David

Thanks for your reply.
Can’t you give me a hint as to why this is happening during the activation of YOUR plugin which I have PURCHASED but can’t use?
Regards David