1/ If Media Encoder is not installed,
Composition > Add to AME Queue option should be grayed out
because if you accidentally click on it, it generates 2 error messages.
2/ A new version is available
If you click the Update button, it opens Creative Cloud Desktop,
and then you can update the software.
The only problem in Creative Cloud Desktop is that when you click on update,
you are prompted to close After Effects to start the update.
So, you have to exit Creative Cloud Desktop, return to After Effects to close it,
and then go back to Creative Cloud Desktop to start the update.
When you click the Update button from After Effects,
you should be prompted to close After Effects automatically,
and then be redirected to Creative Cloud Desktop to perform the update.