mount adapter ef eos-r can't mount 400mm lens

[lordaeron1]

need urgent help, 

just purchased Eos r + Ef adapter and 400MM F5.6 L lens.
Sadly I am unable to fit this lens inside this adapter i don't get it, what gives?
canon website shows that this lens is compatible with this adapter but it just can't fit.
if I turn it harder it moves a little bit even with a lot of force but not really moving at all, pushing it any harder will break it. so I wonder what is going on.

someone please help.

[normadel]

"The strong guy from the Canon shop" shouldn't be allowed near a camera. Is he the owner? Saying "you made me do it" is totally unacceptable. Don't let him off the hook.

[lordaeron1]

He is the manager, i Will try reaching out for the owner. Thanks.