We are very sorry that refunds for accidental purchases and missed deadlines are not possible.
If you don't want to use the license on your current site, you can move it to another site. Please find the instructions here: https://documentation.chattymango.com/documentation/tag-groups-premium/how-to-and-faq/how-can-i-transfer-the-license-of-tag-groups-premium-to-another-website/
That way you can still make full use of the purchased value.
Considering that WordPress issues a new version every few months, we trust that regular updates of plugins help you keep them compatible and secure.