If this issue is not resolved yet, then try flashing the device with another ROM. You probably used a ROM of different variate for the flashings. Usually, most Tecno mobile phones have more than 1 variant for the same model.
There are lots of things you could do to bring it back to life.
1. Check if the problem is from the battery.
2. Check if the problem is from the charger
3. Keep the phone in a hot area to dry out any possible water fro it.
These suggestions are just scratch in the surface. [link redacted by Mod]