Custom Font doesn't work when switching between Mac and Windows

[mbavrules]

I work in a team of architects and half of us use windows, the other half use Mac. We use a team dropbox to hold our files and can open them seamlessly. However, we have a custom font that we all have downloaded in our computers. When I (Mac) open files that other people with Mac systems have worked in, the fonts remain in place. However, when someone who uses windows opens the file, it changes to arial and has a yellow error. And vise versa. It takes a long time to change all the fonts... 

[h_s_walker]

Is it a special MAC font?

Has the font been mapped to Arial (see the two links below)

AutoCAD LT 2022 Help | To Specify a Font Mapping File | Autodesk

AutoCAD LT 2022 Help | About Substitute Fonts | Autodesk

Have the Windows users installed it properly (see the link below)?

How to Install Fonts on Your PC | Microsoft Windows