Hi @pretax ,
After 3 months of not being charged the battery may have become depleted beyond recovery.
First use a strong light and a magnifying glass to visually inspect the phone’s charge port for any obstructions e.g. lint that may be preventing a good electrical connection. If there is anything in the port do not use a metal pin or probe to get it out as it may damage the pins or cause electrical problems in the phone. Try using a vacuum cleaner instead, to suck it out. If it won’t dislodge use a sharpened wooden toothpick to gently prise it out.
You could try leaving the charger connected to the phone for 2-3 hours (if you haven’t already done so) as sometimes batteries can be kick started back into life again. If it shows during this time that it is being charged, allow it to fully charge before attempting to use the phone.
If it is still no good after this time then for a start the battery will need to be replaced.
Here are the ifixit Samsung Galaxy A50 guides. They will help you to replace the battery and the screen.
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