The error says that the WordPress function, wp_remote_post, had an error while attempting to ASN1-encode data for transmission.
Is updating WordPress all you did? Sounds like your server's SSL or OpenSSL library was modified in an incompatible way.
I see similar issues on the Interweb:
- https://wordpress.org/support/topic/wordfence-could-not-get-an-api-key-2?replies=4
- https://wordpress.org/support/topic/error-getting-free-wordfence-api-key?replies=5
Unfortunately this is environmental, and has to do with your SSL library. There's not much I or WordPress can do. I would refer this issue to your host. Sorry :(