SSL Problems

Store URL (if not provided we can’t help much): tilfordwinery.com
WordPress version: 4.1
WP eCommerce version: Custom
Gold Cart version: N/A
Theme: Custom built.

I did this: Earlier I was able access the checkout page as part of a test. When I installed the pricing deals plugin suddenly, checkout page was no longer accessible. And I got this message:

SSL connection error

Unable to make a secure connection to the server. This may be a problem with the server, or it may be requiring a client authentication certificate that you don’t have.
Error code: ERR_SSL_PROTOCOL_ERROR

Tried doing disabling and enabling plugins and clearing out the case but still no progress.

We’re not ready to go live yet but I am wondering whether not buying a SSL certificate would solve the problem? Immediately?

https://wordpress.org/plugins/wp-e-commerce/