New to the forum, can't upload images.

I’m new to blender artists. I am trying to upload some finished work, while starting a thread the upload window opes and the loading sign appears during the upload but nothing happens. A while later I get the message:

"The following errors occurred:

You do not have permission to perform this action. Please refresh the page and login before trying again."

I can’t see the threads that people I’n my situation have posted (a lock icon appearing by them) when I click on them I get the message:

Bad Request

Your browser sent a request that this server could not understand.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.