Here's the Paypal security updates that go into effect in June - https://www.paypal-knowledge.com
. If you don't make these changes you may no longer be able to connect to and process Paypal payments.
SSL Certificate Upgrade
Make sure the SSL for your website has been upgraded to SHA-256. Go to https://shaaaaaaaaaaaaa.com/ to check. If you don't have an SHA-256 SSL, contact your web host to get an upgrade.
Disable TLS 1.0 and 1.1
Go to https://www.ssllabs.com/ to see if you're web server supports TLS 1.0/1.1. If it does, talk to your web host about updating your server. Both of these need to be turned off.
Paypal Standard - IPN verification postback requires https
If you're using Paypal Standard, login to your Paypal account, got to Profile > Profile and Settings > My Selling Tools > Website Preferences, and make sure your Return URL begins with HTTPS