HP Microserver Mini-SAS Cable
I have a number of these servers and it is awkward to disconnect, although it does sound odd you are having this amount of trouble
Tips, because of how the cable is routed and cable tied, also the length of the connector, you need to pull directly up while putting a kink in the actual cable.
The metal clip seems to depress further if you place your finger in the middle. It does latch in to the socket fairly well so getting it depressed far enough is important.
The machine will post without the SAS cable connected so even if you have managed to pull it out slightly, the blue logo should light and the system post. Things that will stop it from booting are having the fan header disconnected (From memory I think that is the cable closest to the SAS connector)
I had this problem yesterday (same server, same cable). Here's how I solved the problem:
Insert flathead screwdriver vertically from above into the central tab.
Push outwards until the central tab snaps free.
Insert paper clip horizontally from the side into the space between the cable & the little metal teeth hooked into it.
Twist the paper clip to extract the metal teeth from the cable.
Repeat for the other tooth.
I've dealt with mini-SAS cables/connectors for years now on a range of HP kit and although they're far from the easiest connector to disconnect I've never had the kind of problems you've seen - I'd advise you to do as they say and get it replaced or call in a HP engineer to swap out the cable, motherboard or both.