Not sure if this has been posted before, but I was able to resolve an issue with the lower third boxes not working. The guide I found on youtube instructs you to enable "local file" in the source properties window. I couldn't get the lower third to show and it would continually have a red surround on the element in the control window. After finding another window that talked about update 27.2 breaking the functionality, I tried to apply the fix, which was to add "file:///" to the file path. Problem was, with "Local File" check-marked, I was not able to edit the file dialog entry.
HERE's THE FIX... DISABLE "Local File". This allows you to manually enter the "URL" for the browser source. So the adjusted steps to implement this plug-in is as follows:
1. Navigate to the browser_source.html file location.
2. Double click on the browser_source.html file to open the file in a browser.
3. Copy the URL to your clipboard.
4. Add a browser source in your scene, title it as you would like.
5. In the URL field for the source type in "file:///" and then paste the URL.
As an alternative, to typing in "file:///" and then pasting, open a blank notepad/wordpad document type in "file:///" then paste the path. Then select the entire text string and copy. Then paste it into the URL field in the browser source properties.
The path should resemble this, depending on where you put the plug-in folder:
file:///c:/Program Files/obs-studio/Animated-Lower-Thirds/lower thirds/browser-source.html
Hope this helps.