While you might have credits available, Social Explosion also requires that you have a valid PayPal subscription in place as well, for a package such as the The Mini Network Package.
If you cancelled your subscription (or it didn't get paid for any other reason) the system stops scheduling any new posts.
Any existing credits you have will remain available in your account and will start being used to schedule your posts for promotion once you set up a new subscription.
Will Social Explosion promote my old posts once I set up a new subscription?
A: No. Any posts you have published while you didn't have an active subscription will not be added into the system or promoted. As soon as you have a new subscription SE will start promoting any new posts you publish again.
My Subscription renewed on the 5th but some of the posts I published on the 5th didn't get scheduled, why?
A: The reason for this is 'Time Zones'. Our system operates in it's local timezone and when you ordered your subscription PayPal set the time/date of your purchase in your local timezone. What this means is that there is a small window where our system is waiting for you to pay by midnight today but due to the time difference our system get's your payment tomorrow. That's why some of your posts don't get scheduled.