Phone not switching on

Good day. I was busy doing a factory reset from the recovery menu. I cleared the cache and then did the factory reset. The phone restarted afterwards as per normal. The phone had the charger plugged in as well to make sure there is enough power. It was busy with the reset, with the progress bar about one third of the way, when the phone just switched off. I am unable to switch it on in any way, including going to recovery mode. Absolutely no responce whatsoever. The screen and all lights remain off. I left the phone on charge for 6 hours. Battery voltage measures 4.08v on my multimeter, so it has charged. Please advise. Phone is a Galaxy J1 Ace. It has never had water damage. My email is bravick1@gmail.com. The phone was bought from Vodacom in South Africa. Regards, Gideon Gouws