Hi,
I am the Windows maintainer for X2Go Client. Sorry to hear that you are running into this issue.
I see that you are using the Windows Client. During the installation, there are 4 sets of fonts which you can chose to install. Which, if any of them, do you have installed? If you did not chose to install all 4 of them, could you retest with all 4 of them installed? Retesting should involve terminating (logging out of MATE) and starting a new X2Go session, rather than resuming the session.
-Mike