User wrote " Hello. I have an issue that occurred after updating to Big Sur 11.6. Sometimes when connected to charging, the charging sign does not appear in the battery icon"
For additional reading on Battery and Apple Computers this link may help. About battery health management in Mac notebooks and especially for the M1 and Big Sur If battery charging is paused or on hold on your Mac
Depending on the Age of the computer, some aspects from the above links, may or may not apply to your computer.
A feature introduced into Big Sur was to preserve the number of Full Battery Cycles - there was an Algorithm coded into the macOS. It is perfectly Normal for Big Sur to Pause / Suspend charging the battery beyond 80% and hold it at that level. One can nudge / over-ride this by clicking the Battery Icon on Desktop Top Bar and allow charging beyond 80%. From observations, it will Pause / Suspend again once reading 90%. Same procedure to over-ride and will charge to 100%