Need help with problems updating Vanilla Forums..??

I see a lot of this, but nothing seems to be helping. I have a server configured with Apache + nginx running together. I have many WordPress sites and Vanilla 2.1.10 running just fine with pretty URLs via htaccess rewriting.

I'm trying to updated to Vanilla 2.3, but when I upload all the new files I end up with 404s. The README mentions that "Additional setup is required on nginx and other platforms" but it doesn't go into detail.

In the forum and other places, I see people talking about how to fix this, and this link seems to provide the simplest method, which is basically to add this to the nginx vhost:

 location /forum
 {
 try_files $uri $uri/ @forum;
 }
 location @forum
 {
 rewrite ^/forum(.+)$ /forum/index.php?p=$1 last;
 }

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Our forum is indeed located at /forum on our site, and we tried this code but it's not fixing the problem.  Any information on how I can get this fixed would be greatly appreciated. Thanks!