PayPal is making some IPN and other changes to their system. If you have received an email about it then don't panic.
Our plugins are ALWAYS kept upto date. You will always have access to a fully working version of the plugin that just works.
PayPal IPN Changes
As of right now, we are using the latest IPN handling code taken from PayPal's PHP code library. If you have any doubt, just load a fresh new copy of the plugin to make sure you are using the updated PayPal IPN verification code:
Regarding the SSL Certificate
SSL certificate is NOT required for our standard PayPal checkout option (the default option of eStore plugin). So if you are not using an SSL certificate now, then nothing to worry (nothing to do for you).
If you are using an SSL certificate on your site then ask your hosting provider to make sure it is "SHA-256" compatible. Decent hosting companies should give you the correct SSL certificate. So not much to worry here.