Why won’t the Panasonic dvd blu ray player won’t open, and how to fix it?

Buy a new one. The cost to repair it would likely be as much as buying a new player.

There's zero chance of getting it professionally repaired for cheaper than the cost of a new player, even if parts are actually available.

Its possible  you could fix it but it might take some patients and understanding on how the mechanism works...I have seen videos on you tube where someone fixes a similar problem.. Probably would be a good idea too seek out those videos and watch them first before trying it..Basically its a matter taking the top off and gently forcing the player to open and close until it does it on its own...You have to be careful though as certain levers must be in a certain position otherwise you could break it further... requiring you to obtain new parts...

Disc drawers are almost universally driven by a motor, belt, and gears. 

Belts often stretch, break, or otherwise fail. 

Most players are constructed in ways that make replacing the drawer belt rather difficult,  

so it is best to have the job done by a professional.  

There are other, less likely, problems that can occur.