I have tried with 3 accounts and a handful of keys in each, and was never able to get anything but 401:
curl -D- \
-X GET \
-H "Authorization: Basic <base64(email:api_key)>" \
-H "Content-Type: application/json" \
Is there some problem with API Keys in Jira?
My problem was with the wrong token because there are two of them: Atlassian Administration -> Settings -> API Keys and https://id.atlassian.com/manage-profile/security/api-tokens
After the token was the right one I got HTTP 405 and that was because of the issue number, as you suggested, thank you!