Messenger scrolling issue

Hello,

For the past 3 days, I haven't been able to scroll back through my Messenger conversations on my PC. The little menu on the right with the scrollbar is gone. I can scroll through the different conversations on the left, but I can't go back through the exchanged messages. Only the most recent messages appear... what can I do? I've already uninstalled and reinstalled it, but nothing has changed.

Thank you for your solutions!