An user in another topic told, that maybe different account (or purchase plan) is the root cause, or at least a workaround.
I tried then by myself.
When i using my business office 365 account, the Copy+Paste function works.
When i logged in with my private account (no plan purchased), the Copy+Paste function doesn´t work.
Maybe this is helpful for you, as a workaround.
This gives me hope, that the function (what is really a basic thing, just copy+paste, i´m wondering, in times of AI, what we are need to talk about) is not killed totally.
Maybe it´s just a bug, or the plan, just keep the function in payed accounts.
Who know´s. Microsoft is silent as always...