You can try to push Power Button really during more than 60 sec, during charge. Sometimes it can unblock some power issues and make a real “hard reset”. I give you this advice like that, no sure it will help but one day I had same issue with an Android device and it solved it : Put in charge, be sure that there is some battery and press power button very long time.
Another solution is to plug it with a Windows PC and try to see if the device is recognized (installing USB Android drivers)
Hello. HI 10 pro would be CWI529 not CWI527. I had the same problem. Battery voltage falled to zero, so you plug the device even if the red LED do not show. The target is to have few % of battery to activate buttons. After a while, maintain Power and Volume + pushed with right hand on the same time and repeat plug, unplug and plug the USB C cable on tablet with left hand. Those actions replace manually the power button action for charging process launch. Then let the device charge while red flashing LED on. Fastboot mode = Power and Volume + , Bootloader mode=Power and Volume - (towards Recovery or Reset)