New HLS stream host(gravlab)/ stream not working

We have a new company doing our streams, Gravlab. The stream is not working. They claim it is not on there end. How can I determine what the problem is? Has anyone had any experience with this company?

the following is the stream url:
http://innovatvnetworks.gravlab.net/hls ... atest.m3u8

Thank you for your help.