Screen went white when I click timeline

The screen went white every time I click timeline.
It’s really difficult to work.
I haven’t used Nuendo for a year.
And it happens…
I’m wondering how to fix it, thank you.

Mac OS 11.2.1
mac pro 2017

Nuendo 8.3.20

how should we know anything?
all I can see it is Nuendo 8

Hi, I just reply.
Anything else I should provide?
Thank you so much.