When Microsoft included Arial Unicode MS with earlier versions of Office, Microsoft paid a licensing fee to The Monotype Corporation, which is the copyright holder for the font. Starting with Office 2016, Microsoft no longer pays that fee so it was removed from the Office package.
In order for Connexion client to be able to use the font, ARIALUNI.TTF file (the Arial Unicode MS font) needs to be in the PC's Windows\Fonts folder. It is not included in any version of Windows. It needs to be imported. If you have it in a Windows 7 (or Windows 8/8.1) Windows\Fonts folder from an earlier version of Office, you can copy it from there to your Windows 10 Windows\Fonts folder.
After it is installed, you should see it in fonts on your PC at Start > All Programs > Accessories > System Tools > Character Map. Or, click Start and search for character map.
If you do not have an existing Arial Unicode MS font available, the Google Noto Unicode fonts work well and are free.
Click for help installing, and to download the Google Noto fonts for Windows.
Click for info on the Microsoft Arial Unicode font which now has to be purchased.