Please use this option only in case you are debugging and you can't wait for the request to be processed regularly by cron job.
If the application is set to use cron job then it takes 2-3 cron job runs to process the tracking requests. Hosted with us accounts always use cron job and it takes 5-15 minutes for the tracking requests to be processed. Usually, if you are debugging the tracking you do not wish to wait so this guide is for you.
Self-hosted customers, please remember that if you are NOT using cron job then you should NOT do this. You can find whether you are using cron job in Tools->Integration->Cron job integration. If you get a message Cron job is not running then do NOT continue.
You need to go to Emails->Mail outbox and click the Send pending mails button. It opens a window with Pending Background Tasks where you need to find Visit log processor and click the green refresh icon next to it twice: