When an order is not exported to your webshop, then the most common reason for this problem will be that your webshop hasn't accepted the order. That can happen due to multiple reasons.
Good to try
The best thing to try first is to see if you can place the order on your webshop itself, with the same products and customer data as the order contains. Maybe the customer lives in a country, your webshop doesn't accept, or maybe the minimum order quantity of your product is higher than what the customer ordered. Please keep in mind that the product does also needs to be enabled in the correct store view (if your webshop uses multiple store views).
Tip: Did your client fill in an address or country that your webshop does not support? Then temporarily change your conditions in the webshop and export the order again.
Another way of solving this problem is to change the customer data in the order in EffectConnect so it suits your conditions of the webshop, and then re-export the order. To edit customer data, open the order in EffectConnect and click on the button 'customer data'. 
After changing the customer data, you can re-export the order.
To read more about exporting orders, click here.
Check the error logs
In most situations, you will find an error log in EffectConnect, if your webshop gives us the reason for rejecting the order. It can occur that the order isn't exported because it contains a certain tag that blocks the export, or is blocked because of a queue rule.
Good to know
Are you using a Magento 2 webshop? Then keep in mind that Magento works with cronjobs which perform the synchronizations. A cron job is a scheduled task, which is usually repetitive.
So there is a cronjob that automatically retrieves the orders from EffectConnect. Is this not happening? Please check whether the cronjobs have been successfully set up. You can't figure it out? Please contact your IT department.
Are you using a custom API connection? Then please check your credentials in EffectConnect and your own software. Is the secret and public API key the same? For more information about our API, read this article.
Once you found the problem and solved it, you can re-export the order to your webshop.
If you need any assistance regarding exporting orders, please contact us. We're glad to help you out.