You cannot copy/paste the seed, you literally have to type it in but probably you didn't save the file.
That's not entirely true... What happens is that Electrum simply blanks out the clipboard when you click "next" to goto the seed entry screen, so if you try copy/paste, you'll end up "pasting" an empty string into the box...
Unfortunately, what happens is that if you click "back", Electrum will actually generate a completely new random seed... invalidating the previous one.
(Sidenote: I have a suspicion that this may explain how some people end up with multiple seeds written down or copying down the wrong seed etc.)
Anyway, what you can do to copy/paste, is that you can first copy/paste the seed to an external application (like notepad etc) and then click next... the clipboard gets wiped but you can simply go back to the external app and copy the seed from there and then paste it back into Electrum
Almost sure that if the version of electrum I used required the seed phrase, I did something like Next/Next/Next/Accept (yeh, I didnt care much back then)
Electrum requires you to re-enter the seed to confirm it... so you can't just next/next/next/accept etc... you would have had to have copied the seed and then either typed it back it manually or used the hacky copy/paste method I described above
Lot's of users in the past have copy/pasted into .txt documents, or taken screenshots... and ended up losing funds as a result of this... but, poor security practices aside, TheBeardedBaby was simply suggesting that you might want to look through any recovered .txt and image files to see if maybe you had done something similar. It's not guaranteed, but it's worth a shot.