Dashboard widgets won't update (Stuck at "Updating in 10 seconds")
When upgrading between major versions of pfSense, a condition can occur leading to the Dashboard widgets not updating properly. The most obvious symptom is the CPU activity being stuck saying "Updating in 10 seconds".
There are three ways this can happen.
Leftover File from Upgrade
One way this can happen is if a file (sajax.js) is not properly removed during the upgrade, or is re-added after the upgrade process has cleaned up.
The only file that should exist in that directory is "ajax.js"
Ad Blocking Add-ons
If the browser has an ad blocking add-on such as AdBlock Plus, it may be blocking the AJAX update call because it's fetching getstats.php, which it believes (incorrectly) is for ads/tracking.