Cannot enable external storage in Nextcloud 16

I have just installed NextCloud 16.0.1 on a Centos 7.6 VPS with php 7.2

Installation seemed to go well, but if I try to enable external storage as admin, I only get this error:

"smbclient" is not installed. Mounting of “SMB / CIFS”, “SMB / CIFS using OC login” is not possible. Please ask your system administrator to install it.

I installed libsmbclient and php-smbclient, and restarted apache, but nothing changed. What should I try next? Thanks

Perhaps you have to enable the module. You can use a php testpage to check the configuration and the modules used:
<?php phpinfo(); ?>