In a long thread, I started clicking on the automatic translation button on each post. After about 3 posts, it stopped working, with the message

You’ve performed this action too many times. Please wait 44 seconds before trying again.

Maybe this is an upstream rate limit that cannot be removed. Anyway, copy and paste into translate.google.com still works.

This is plugin limit, not an upstream limit.
I’ve created a feature request in the plugin forum: https://meta.discourse.org/t/feature-request-make-rate-limit-configurable/129589
And I think I’ll patch it for you.

Should be fixed now.