Firstly I hope you're both well and thanks for this free extension. It's a great addition to a site combined with the power of social integration from JFBC!!
I've recently setup a Sendy installation with a custom domain inorder that newsletter links appear as a newsletter.domain.com subdomain. I've installed the sendy integration package, published the plugins & module and populated the details of 1 list in the plugin, and the API key and list ID in system plugin.
My module is published but upon hitting subscribe, I get the following error:
"Uh oh! We encountered an error when trying to sign you up:Unable to decrypt string with openssl_decrypt()".