Colin
Grrrrrrrrrrrrrr!
I thought that it was sorted but it isn't. I logged in to Model Boats Forum this morning and posted to your new forums problem thread. All went well and before I left the forum the post was clearly there. I have just gone back to see what else had happened and my post has disappeared. The least post is yours 23rd Jan 16:51 which is on page 7.
I had done a video of my log in etc but as it worked OK got rid of it.
My belief is still that it isn't about the browser that you use but rather about the security & privacy settings within the browser. The Model Boats forum seems very sensitive to this compared to anywhere else that I go.
If it helps I will message my settings but I don't really want to put them on the open forum.