Why is a new post not shown in the Latest Topics Block after updating Advanced Forum?
Some problems get resolved just by being patient for a while. Some of those problems are caused by either of the following:


You should have cleared the cache.
Something required a cron job to run.


If such kinds of actions are not performed (eg because you're not aware they are needed), it is just a matter of time to get such problems resolved automagically ... as illustrated in this specific comment (last paragraph) also.