Validate/Duplicate Font Issue (Open Sans is displaying incorrectly on PowerPoint)

Hi there!

I hope someone can help me out with this...

So, I have been working with the Open Sans font on PowerPoint for the past three days, as it is compatible with both Mac and PC software (and an approved font at the company I work with). I use the most recent version of Office for Mac btw. Anyways, today I go into the saved ppt and the font is totally different. It looks like a type of Sans Serif font now (but displays as "Open Sans" in the Font tab). To troubleshoot, I tried 'Replace Font' but I couldn't do this since Open Sans is no longer showing up on my Font List and was nowhere to be found in my Font Book.

2nd troubleshooting attempt:

I tried to download Open Sans for Mac and install it on Font Book. Theres a few varieties included in the file, but only one (Open Sans Light Italic) was validated. The others had warning symbols next to them. When I checked the details of each, the warning symbol was next to 'Duplicate Font'.

I tried resolving this by clicking 'Remove Duplicate Font' but nothing happened.

Anyone else run into this issue?

Please help!