Where do you find the access code? Is it something you make up?
I also had the problem with "Mybb Not Found(check URL)" on the options page. Then the similar "(check code)" once I fixed that. I've tracked it down to two problems.
First, in the wpmybb.php plugin for Wordpress, within the post_it function, the contentlength doesn't account for the trailing whitespace when it should.
Line 354 should be:
$contentlength = strlen("$reqbody\r\n");
instead of: $contentlength = strlen("$reqbody");
Second, in the wpmybb_bridgemybb.php on the MyBB side, the access code check doesn't allow for possible whitespace which tends to get into post variables for some reason. So...
Line 13 should be:
if($mybb->settings['wpmybb_accesscode']!=trim(get_post_var('ac',true)))
instead of: if($mybb->settings['wpmybb_accesscode']!=get_post_var('ac',true))
With those two fixes, the config in Wordpress is now working for me (although I have to check if the rest of the plugin works, I haven't configured my Wordpress theme yet).
Also, I'm not certain, but do inline replies require the domain to be the same on the Wordpress site as the MyBB site? The plugin seems to use the MyBB cookies via the Wordpress. My Wordpress blog is on a different domain than my MyBB forums.
looking forward to new release
mine is currently offline until this is ready to go
I'd like to thank Hangman for his great support and help fixing my problem with this bridge. Now that it works, I'd like to say how great this plugin is. Thanks for making it.
Hangman's Plug-in works great! Can't wait for the "merge" users option.
I'm still having the MyBB not found error after applying Rog's suggestions. I'm on MyBB 1.2.9 and WordPress 2.3.1.
I attempted to hardcode my URL into the code. Not sure if I replaced the proper variables, but it still would not grab any data.
Edit
Got it working with Hangman's help. I think the problem was either with Apache or PHP on my other server.
Hangman Wrote:Just started working on it after one and half months. 
Could you guys post the URL of your websites that use WP/MyBB?
I would be glad to see it in action! 
My blog:
http://rog.gameslate.com/
And the corresponding forums from the bridge:
http://path.gameslate.com/forums/forumdisplay.php?fid=9
I must say, after using it for about a month now, I'm extremely pleased with this paradigm. I love Wordpress for blog postings, but the Wordpress comment system has always been sorely lacking and has so many holes for comment & referral spam.
And .. I have another request:
Is there any way to turn off HTML filtering for posts made by the Wordpress bridge? Actually posting seems fine, but it's later edits that filter certain things out.
For instance, if I make a post that includes the embedded object code for an inline Youtube video, it posts via the bridge just fine, but subsequent edits will remove the code for the video. The removal is both ways across the bridge btw, it removes it on MyBB and Wordpress.
I've had similar troubles with CSS classes that get filtered/removed from HTML too. In these cases, I've had to turn off the bridge plugins temporarily to fix the posts.
Hangman Wrote:WP/MyBB uses the MyBB cookie on the WP side to get logged user's info, not for posting.
I didn't think about the fact that this can cause problems with WP and MyBB being on different domains - I'll try to fix it in the next release.
Cool, I'll look forward to that. For now, I've just provided a link to the forums for replies rather than have them inline.