Toilet Plastic Ballcock problems

Hi,
its a 5 minute job I told the Missus. The ball valve was sticking. I bought a new one - they're cheap and I thought it would be quicker. Its a bottom entry cistern.

Nowe it may be obvious, but I could not get it to seal. The pipe work feeding the cistern was standard copper pipe with a compression nut on it. There was no olive, wacher or anything. Not sure how it ever sealed. I think I've probably bust the valve assembly now as I think I've overtightened. Plastic is fragile.

What any I doing wrong. Can you still get good old fashioned metal bits still.

or most probably cross threaded it

new ballvalve and a bit more care and you should be grand

Did the connector look like this?

If so there shold be a fibre washer that fits between the connector and the cistern valve. This may have stuck to the bottom of the old valve or may have perished.

You may need one of these