Add Media Button Not Responsive

Activate the twentyfourteen theme.

And can you please disable all plugins.

Check your editor again if the media button is working and post a link to your site.

I’m not sure this is related, but I also don’t get the functionality described in the video wherein the toolbar remains visible when scrolling down through long texts on the page.

in Screen Options if you uncheck “Expand the editor to match the window height” the scrollbar will appear again.

I activated the twentyfourteen theme and the button now works (but the site looks awful!): https://www.orionmcu.com

Where do I find the “Screen Options” checkbox?

My “Screen Options” link on the desktop provides the following checkboxes only:
Show on screen:
At a Glance Activity Publishing Help Quick Draft WordPress News Welcome

Where do I find the “Screen Options” checkbox?

go to your post/page editor in the admin and check your screen options at the upper right.

I activated the twentyfourteen theme and the button now works (but the site looks awful!):

Unfortunately, it was your theme causing the problem. I can see you didn’t deactivate your plugins, but it is obviously your theme…

So now you’ll have to contact your theme developer to see if they have an update or fix so it will continue working on 4.0.

If you don’t know where the theme came from, go ahead and activate it again and I’ll try and help you locate a contact for it.

I had to reinstate our custom theme since without it the site was unusable. Now the Add Media button works!

However, I am still interested in the fixed position for the toolbar functionality. Please advise how I can enable it.

not sure what you mean by fixed position of toolbar.

Did you find the screen options in your page editor and try unchecking the box that says “Expand the Editor tomatch the window height”?

As part of the new features in “Benny” I understand that the editing toolbar remains visible even when scrolling through long texts on the page. This is not the case in my implementation.
My “Screen Options” link does not include the feature you noted “Expand the Editor to match the window height”
It provides the following checkboxes only:

Show on screen:
At a Glance Activity Publishing Help Quick Draft WordPress News Welcome

Do you think this problem may also be related to the custom template I am using (Flagship)?

try switching your template to the 2014 and see.

I am afraid of switching the template since that move corrupted some settings. I will just wait to see if the custom template developers can improve their support for Benny. Thanks for your help.