bootstrap (website) on cpanel not working well with www

I got a problem, maybe is related to CNAME or maybe to .htaccess file. website is working well if we use domain.com for example without www For example: http://domain.com is working well

but if we will use www. domain.com some part of website like css related to bootstrap icons will be disappeared. for example:

http://www.domain.com still website will be loaded but not working well.

Anyone who faces this problem, please share your knowlege how to solve this issue. Maybe we can use to force through htaccess to redirect to non https or http but in this case, how to make it work with www. ?

Thanks in advance