Lighting Issues

This question is for all of those people who have experienced the similar problem I have experienced

When placing lights into my drawing they worked initially and they worked very nicely. Afterwards while I was continuing drawing, the lights stopped working. I added more lights and these as well do not work in this drawing. However they work very well in brand new drawings.

Could my problem be that I may have change something by accident. Like a scale or something
I'd like you guys to help me out here

First you need to check your lighting settings in the dashboard and make sure it is set to viewport /users lighting and it is on.Also check the prop of the light and see what intensity is set to.Let me know what happen