The health assessment of batteries for Macs with Apple Silicon may be shown as “unknown”: If you are using a portable Mac with Apple “M” processor, the line Assessment in the section Battery Health might sometimes be indicated as being unknown, instead of showing the true value. This effect can vary depending on operating system version.
Workaround: This is a known defect in some versions of macOS. Update the operating system to macOS 11.6 or later to get more reliable results. If this still doesn’t help, restart the computer.