Apache virtualhost no prefix

Hello all,

I have a host with apache and virtualhost set by servername tryhard.com

I tried 2 kinds of settings : one with reverse proxy + prefix: ok
so If I go to tryhard.com/prefix  --> ok

I made a subdomain: uboo.tryhard.com (set 80 for Ubooquity)

Tried to set apache to reach it but it failed. But According to apache documentation, we can set the reverse proxy like that.

ProxyPass / http://localhost:80

But It does not work.

Is it possible or did I miss something somewhere ?

Thanks a lot

Regards