Unavailable Font Error

We have  a team of close to 30 people using FM templates that uses Open Sans. Ever since we started using Open Sans we get the unavailable font error. This happens when we generate the TOC or use the Find tool. We checked all the font folders that Frame uses and the Open Sans fonts are correctly installed. We also unchecked the missing font alerts and remember missing fonts check boxes under Preferences and the error still persists. As a workaround, we have people open all files in a book before they publish or use the TOC or Find tool. This has helped, but if Adobe can recommend a permanent solution to this issue, would appreciate. Thanks.