At our site [url removed, login to view] we have our site communicate with the eBay API in order to do 2 main things:
1. Post our listings to eBay from our site according to our inventory.
2. Have eBay send order information back to our site so that orders can be downloaded when ready to ship.
It may be important to note that our site also takes orders, and when orders are placed on the site through Google Checkout, those orders are also sent to the order download page on our site so that we can download them when ready to ship.
People can still order on our site and orders are still sent to our download area on our site but...
On the 15th of February something "broke." We are assuming something simply changed with the eBay API. Orders that were made through eBay sometime on the 15th stopped being sent back to our site.
It wasn't til about 15 days later that I also realize that our site stopped posting listings to eBay through the API. I noticed this when our listings finally ended. Now we have nothing listed in our eBay store at [url removed, login to view] when we usually have a few hundred listings.
Something breaking with our set up has happened in the past, and our guy that helped us set things up was able to go in and see which portion(s) broke. It always seemed to be simple fixes that would only take a few hours to find and finally fix. Unfortunately our guy says that he no longer has time to help us out due to his new full time job.
Basically we need someone that is familiar with eBay's API (at least somewhat) that can jump in and find what's broken. If you visit our site you'll notice it is written in PHP. Our site is http://www.rockitrigs.com.
I believe MySQL databases are being used with this whole site/eBay API integration. I'm not 100% sure how everything works though because I am not a programmer. I only know how to put together simple websites. The special features for this site were created by our former guy who now is too busy with the full time job.
I specialize in eBay API and would gladly take a look at your problem. I don't think eBay has done any major changes to their API in February, therefore something might be wrong on your end.