My Macbook won't turn on unless plugged in.

Hello, today I took my machine (MacBook Pro (13 inch), no Touch Bar, 2017) back from an authorised repair shop, where they replaced the keyboard under the butterfly keyboard replacing warranty. The keyboard is replaced alongside with the battery and the lower aluminium frame. Everything worked fine in the store, but 20 mins later at home the computer didn't start. I connected it to the charger and after a few tries I got it to work. However, I had some very unusual symptoms:

-The computer can't stay on unless plugged in to the power, as if it was a desktop computer.

-Fans are loud and seem to be working at high speed regardless of temperature, and do so from the very moment the computer starts.

-Keyboard backlight is off and its control keys are unresponsive. Screen brightness is fine.

-Battery status doesn't appear on menu bar. Went to settings to manually activate it but it just pops in for .5 seconds and then disappears again. I managed to click it once before it left and it showed a crossed out battery icon, as if the computer didn't recognise the battery.

My best bet is that the battery simply disconnected on the way home due to bad luck. Tomorrow ill get it checked at the store again and see. If someone knows what's wrong, please tell. I will follow up on this with the cause as soon as they tell me exactly what happened.