So the new frame for my E+2 arrived (now a green one), went for a ride and all good. But to my surprise, after going back to remove the battery to charge at home, undid the locking bold but it won't come out

I can maybe nudge it a couple mm forward at best, totally stuck. Before I take it back to the shop, any ideas what might they have done wrong? In my old frame, once I opened the locking bolt the battery would fall out, always had to have my hand underneath it to prevent it from hitting the ground.
I have no power source in my building's storage room, removing the battery to charge at home is a must for me