Powerpoint Restricted Font Issue

Hi All,

Anyone else encountering a Restricted Font issue on Microsoft Powerpoint which has only arisen in the past month? We've been using a custom font for a corporate client for the last 2 years without any issues but as of about a month ago, Powerpoint has started flagging that the font as 'restricted' and the file (which I created) is now only 'Read Only'. I am given the option to remove the restricted fonts (defaults to Calibri) and open an editable version of the file but this is not possible as we need to use this font. We've tried updated operating system to the latest OS Monterey (previously on Big Sur). Powerpoint is also updated to the latest version 16.63 and no luck. The strangest thing is that sporadically, the font will work, but most of the time, it shows the issue below. (Sorry for confidentiality, I had to cover the font names). We've found that the issue doesn't arise on old versions of PPT (like 2016) but thats no good to us either.

Any help would be greatly appreciated.