Error 404 on all subpages

Hy,
A friend of mine ask my help to upgrade his hosting (NameCheap) and install a custom crm for specials needs on his website.
Everything during the installation work fine, but now all the subpages including admin returns error 404. I checked permissions everything seems alright. I check routes everything seems alright too.
I’m not a specialist of CodeIgniter, need your help to find the solutions.
If you need a more informations, please ask.
Greetings