How to solve "Permission denied" when changes root directory

I have followed this [How to] How to build Jitsi Meet from source: A developer’s guide - Developers - Jitsi Community Forum - developers & users to run the jitsi from development source code.
But when I change the root directory it shows permission denied.

Please help me out

The web server (probably www-data user) has no permission to access this folder. This is a basic Linux issue, not related with Jitsi… Checking some documents related with Linux file system may help.