In order to post in the forums, you need to have a registered user account, have activated your account by clicking on the activation link in your email, and be logged in.
To start a new thread you must be on a particular forum page, not the main forum page. To reply to a thread, you must be viewing that thread.
If you are certain that all of these conditions are true, there are a few other considerations, as follows:
Regular users cannot post new threads in the main news forum or the forum for political news:
You won't see a Post New Thread button in these forums. Only MacRumors can create new threads in these forums, but all registered users can reply to posts in threads there.
The following forums have a minimum post count requirement:
Political forum requirements:
Only users with a history of 100 posts and membership for at least 1 month can post in the Political News
If you start a political thread in another forum to avoid this rule, your thread will be deleted or moved.
Marketplace forum requirements:
Only users with a history of 250 posts (user title 6502
or higher) and membership for at least 6 months can access the Marketplace
If you start a "for sale" thread in another forum to avoid this rule, your thread will be deleted.
Reaching the requirements:
Once you reach the required number of posts and length of membership, you may not immediately be able to post in these forums. The privilege is added automatically when the forum system does routine processing, so check again tomorrow. The delay is normal, so please do not contact us to report it as a problem on the same day that you first meet the requirements.