'firebase' is not recognized as an internal or external command, operable program or batch file

Ok. First of all, Bizarre problem has some bizarre solution. Uninstall your node js and NPM completely. Then reinstall it, and check, whether it works or not. Best of Luck

add to .bash_profile export PATH="$PATH:/usr/local/bin" and run

npm install -g firebase-tools

this worked for me

npm install -g firebase-tools -f

Using -f for force install again. This work for me