If the error is
Error: Node Sass version 5.0.0 is incompatible with ^4.0.0
Step1: stop the server
Step2: run commands are npm uninstall node-sass
Step3: check node-sass in package.json
if node-sass is available in the file then again run Step2.
Step4: npm install [email protected]
<=== run command
Step5: wait until the command successfully runs.
Step6: start-server using npm start