Only admin can comment

Most peculiar. Almost from nowhere, have noticed that if anyone (including people registered) wants to comment on my blog (https://www.simonwaldman.net) the comment doesn’t get posted – and all that you get is the comment form back, but with the comment removed, if that makes sense.

However, if I – or a user I have set as admin – post a comment it’s fine.

I have checked and double checked my options – and I cant’ see what might be causing it.

I’m sure it’s something simple I’ve overlooked..all suggestions welcome.

Thanks

Simon