Cannot see RAM Metrics for Linux VM, even after enabling guets level monitoring

Hello

I would like to monitor the RAM usage of my Linux VM. I enabeld the guest monitoring like described here.
But I do not have the Guest (classic) metric namespace avaiable. I already removed and readded the guest monitorning and waited a few days but still not able to see RAM metrics. What do I need to do to get the RAM metrics for my VM?