If French trademark law is even remotely close to US trademark law, it can't be applied to videoconferencing because you can't apply a trademark that is just the term for the category of product that is covered.

So for example, I can't trademark "Apple" for my apple orchard. But I can trademark it for my computer company. Similarly, MS likely has chart visualization tools covered by "Visio" in France, but not telecommunications software.

Trademarks aren't granted to a company for unrestricted use. They're granted for specific use. Like I can't found a computer company, get Apple trademarked, and then buy an orchard, use Apple for the orchard, and then sue every apple orchard for saying "XYZ Apples" in their name. It remains restricted to a specific use that was included in the initial application for TM.