Track changes not being shown in project file after reviewing?

Hi,

We are having a problem where a reviewer sends an sdl project back to the translator with track changes and when they open it, track changes are not visible. We tried opening it on another laptop on our side and it opens up fine - track changes are visible. How do we solve this? On their end, they confirmed that they are opening up the project, selecting all sdlxliff files, right clicking and selecting open for review. They also tried using filters but nothing seems to be working. Track changes button is also on. Has anyone had this problem before? This is happening with two of our translators.