Why is there not enough memory to run a Hyper-V WIndows 10 virtual machine?

Question

Windows

I have an Ubuntu Virtual Machine with Dynamic Memory in Hyper-V. In the settings of the virtual machine, RAM 4096 is installed. On the laptop, about 5GB is free at the time the virtual machine starts, but Hyper-V constantly gives an error that it is impossible to start the virtual machine.
What could be the problem? Moreover, earlier it was launched even with 4.5 GB free, but now it does not want any at all. What could happen? And how can this problem be solved?

Answer 1

Where to give a virtual machine 4GB if you have only 8?
Limit virtual machine memory.

Answer 2

so you also have a dynamic memory checkbox, in the range from 512 to 1048576
uncheck it so that the machine uses strictly 4096 specified