I have setup dispatcher with vanity URLs configuration so that it can allow the vanity paths whenever they are created by authors. I have installed the necessary package on AEM instances and given read permissions to anonymous on the vanity list URL - /libs/granite/dispatcher/content/vanityUrls.html.
When I configured this with dispatcher and restarted it I saw that it created the vanity urls file under /tmp with the list of all available vanity URLs. But if I create new vanity URLs in AEM then they are not getting added to tmp file and dispatcher does not allow it. I have checked the permissions on the tmp file and apache has permissions to write to that file. If I delete the tmp file and restart dispatcher then a new file gets created with a list of all available vanity paths but the file is not updated when I create new vanity paths.
Version of AEM - 6.1 SP1
Dispatcher - 4.1.11 on Apache 2.2 (installed on windows server)
https://docs.adobe.com/docs/en/dispatcher/disp-config.html#Enabling Access to Vanity URLs - /vanity_urls
From the doc
"When access to vanity URLs is enabled, Dispatcher periodically calls a service that runs on the render instance to obtain a list of vanity URLs."
When you increase the log level in Dispatcher are you seeing this request and do you see the corresponding request in AEM, what is your delay set to?
This feature has a /delay setting. They must set that in seconds. I think the default is 5 minutes before the vanity url list would get updated.