My order number is 891906755591016 my name is Jennifer McClatchey. I received a brown backpack. I tried to connect shoulder strap and the hook broke in half. Please help me I need a refund.

go to a stihl service shop and get the parts there

Try going direct to supplier or ebay

http://www.emscogroup.com/customer-service/
I called the customer service number and spoke with a representative who asked me to send her a picture of our board. On receiving my photos she is going to send out a new strap. I'm sending the photo shortly.

You have posted in the car and truck repair help section. Please repost so the correct expert can help you.

The sternum strap only purpose provides stability and keeps the shoulder straps in place.

It appears that the one worn across your back is sufficient. Here is yours:
http://www.ereplacementparts.com/harness-assembly-p-519878.html

look in local retail stores and see if you can find one like your car seat, and tell them your situation and ask for owners manual and get repair, or order parts phone number in the manual

There should be metal hooks on the backside that hook onto the loops at the end of the shoulder straps. They will definately be metal so should be easy to spot against the plastic back of the car seat. They usually are sort of rectangular and have one side that has a 'lip' so the straps aren't supposed to just slip off. (Though I can imagine the possiblity of this when the belt is not stretched as it is during use) Refer to your manual if you cannot find them. If you no longer have the manual, you should be able to locate one for downloading or viewing PDF file at the manufacturers website. Hope this helps! :)