Why is my tablet not charging?

Either the charger has given up/died, the cable has, or the socket and charging circuit on the tablet are at fault. Changing the cable with new or known good is a trivial try at a fix. Testing on other devices, then if failed pening up the (unplugged!) charger to look (perhaps with a suitable multimeter) for leaky capacitors to replace or absence of voltages on a test bench where there should be voltages ought to help cover the charger case. Once that's sorted, if your tablet won't be satisfied to charge (even if factory-reset after a minimal charge to remedy soft errors in charging logic) then the tablet's good to open up, have its battery unsoldered and tested separately (with a bench charger!) and perhaps have its charging port replaced with one that isn't bent out of shape and connections.

Then to XDA forums for a reasonable ROM image to put on it (and the technique to do it by!) before you close the case! Failing that the Intel chipset makes it reasonable to make an embedded ROM yourself.