Thanks for reaching out to us. Geekbench 5 does require macOS 10.13.5 or later, while Geekbench 4 supports macOS 10.10.5 or later which might make it the right choice for you. You can find out more about Geekbench 4 on our website here.
I've issued a refund request for your purchase of Geekbench 5, and the license should be refunded soon.
Please let me know if you have any questions or concerns.