Hi folks,
I had the same “blinking red light during charging” symptoms on my Huawei P8 Lite with a completely flat (0%) battery. I guess this happens because Android requires a minimum level of power (2-4%, below which the phone automatically turns off) in order to control the charging process. What I’ve tried and helped was leaving the phone on charger for cca. 10 mins and after that I performed hard reset (pressing and holding Volume UP + Power keys simultaneously - the method may vary for other phones), just like when you want to wipe cache data. And voila, the phone started to boot and charge normally.