Browser instability or large amounts of data cause your QuickBooks Online Accountant (QBOA) to block pages from loading correctly, Manisha.
To see if this is a browser-related issue, let's start by signing into your QBOA account using a supported browser or clearing your browser cache. This will disable the extensions and stop the cache from saving your search history.
Next, you'll want to restart your browser and log back into your account to verify if the courses in the Training tab are appearing as expected.
You can also take a look at this resource to learn more about tools exclusive to QuickBooks Online Accountant users: Learn about accountant tools.
You can reply to this post anytime if you need more help.