Thanks again.
I have already reverted to an unedited theme and deactivated all plugins, the error still occurs ( mainly for USA visitors )
It’s looking like a clean wipe of everything and starting again is my only option.
I can’t find anyone with a similar issue anywhere.
Thanks for your reply.
I’m not sure what region / country you are located in, but if you click the login link on my site, do you get a 404 error?
The problem popped up randomly, and many users were able to comment and login previously, but are now unable to do so.
I am at the point where, I might have to remove the entire site, and start again.