If you've just posted a review to either of the review fora, then it will take some time (usually between a few minutes and a few hours) until it will appear. This is because a moderator has to approve it.
If your review still hasn't appeared after (say) a day, then this will be because of one of a few reasons.
You have no email address in your profile.
Personally, I won't approve a review of any band, critical or otherwise, if I don't have any means of contacting the person if someone complains to me. This means that I need to know you personally, or there needs to be an email address in your profile.
To put an email address in your profile,
(1) Click on 'My Control Center' [sic]
(2) Click on 'Edit Profile'
(3) Check 'Publicize email address'
(4) Click 'Submit Changes'
If you really don't want to publicise your email address, you can email a moderator about this.
If it's your first ever post, and your email address is something like email@example.com, you may meet with some scepticism.
You are reviewing your own band.
Don't do this, basically. If you were one of several bands on a bill, feel free to add something like 'we played a great/@#%$/pissed gig', but don't write 16 paragraphs of text on yourself. If everyone did this, then noone would read the reviews board, and what would be the point of it? If you really want to post something like this, by all means do so, but use the main forum.
If we think you are a member of the band reviewing yourself under a false name, we may or may not approve the review. Bear in mind that it's usually very obvious if someone's only post is a fantastic review of band X. This may be more damaging than you think. Here is a [url=""]great example[/url].
Your review is too short or pointless.
You don't have to write pages and pages. But do describe why you did or didn't like the band. Reviews of the form 'Saw this band - they rocked' will probably never be approved.
The moderators are lazy.
If none of these things apply, then feel free to mail a moderator, or post on the main board. You should get a reasonably helpful response...