MacBook Pro

Let it charge overnight ...or all day long.

If the battery self discharged to the point of total exhaustion, it may be damaged. But leaving it on charge may bring it up to full power. You'll just have to try it and see.

If it does not take a charge after sitting all day or night, you need to take it to Apple for examination. September of last year means the Mac is likely no longer covered by its one year warranty. Being this is September, it'll be close.

if you didn't buy the extended warranty, you'll be responsible for repair costs. if there are any; it may charge just fine ... it may not.

ku4hx advice to connect it to charger and let it charge overnight or over-day is spot-on.

On older Intel Macs, charging is handled by the System Management Controller, a separate microcontroller that does such housekeeping chores. On an Apple-Silicon Mac, there is no separate microcontroller -- one of the low power processors does that work. If the power drop so low that everything halts, you can only charge at the trickle-charge rate until the power level in the battery returns enough to power some things back on again.

When power returns to that level, one of the the processors can wake enough to request a higher charging rate from the power adapter, and everything will perk up -- if it is going to perk up without more intervention.

Get Apple Care on that Mac, and take it to Apple to check out.