Is my Chromebook done for

Hello, I have the Lenovo Ideapad Slim 3 Chromebook, It's about 2/3 years old

Last year I stopped using it and I haven't powered it on in probably six months by now

I've tried plugging it in now with a 45W laptop USB C charger and the light next to the charging port keeps flashing red and yellow in an irregular pattern

Does this mean the battery is dead or do I just need to leave it to charge for a while

I know absolutely nothing about technology so any help is appreciated, thank you, it'd be nice to not have to replace this laptop