Only I can see the posts, nobody else can.

Several things could be responsible for this. It could be your default privacy settings, your app could be “Sandboxed”, your posts could have low priority, etc.. First of all check if your app is not “sandboxed”: Facebook->Developers->Apps->Your App...

SSL/https/certificate related issues

This error means that cURL is misconfigured on your server. Most probably curl ssl(or openSSL lib) is broken or it simply can’t find the certificates at the pointed location.Please contact your hosting provider and ask them to turn on or FIX “client side SSL” for your...