Applying theme to all users

Hello all,

I created a new theme for our environment in UI16 Istanbul. I found a great article explaining "how to apply to all users", which was editing Company and including the new theme.

The problem is that we have 242,653 users so it seems the theme is not being applied to all users. Would this be because we have a lot of users? I tried the same method in my demo instance and it worked. Has anyone had a similar issue?

Thanks in advance,

Grace