Hello,
Thank you for letting me know. The free plan should be sufficient.
The API keys, including the one I currently have, used to be 32 hexadecimal digits. It seems that with their switch to API layer, they now use the entire alphabet.
There is a regex validation on the API key, but it’s only applied on the frontend. The value you entered as an admin is not validated on the backend (except for SQL injections, of course).
I will patch the plugin. In the mean time, you can delete the following three lines from your code, and you will be able to enter your key:
https://github.com/dashed-slug/wallets/blob/6.0.0-RC1/admin/settings.php#L794-L796
You can find this file at wp-content/plugins/wallets/admin/settings.php.
Thank you for providing screenshots. I have deleted the screenshot displaying your personal key from this public forum.
with regards