Les deux serveurs ne communiquent pas ensemble vérifier vos firewalls et votre configuration LDAP.
Si le problème persiste envoyé un impression écran de votre page système.
[Thu Jul 25 14:12:42.911161 2019] [:error] [pid 21232] [client 10.10.31.50:52182] PHP Warning: ldap_bind(): Unable to bind to server: Can't contact LDAP server in /var/www/gestsup/core/ldap.php on line 117, referer: http://gestsup.opacoise.fr/index.php?page=admin&subpage=parameters&tab=connector&ldaptest=1
[Thu Jul 25 14:31:57.076560 2019] [autoindex:error] [pid 26025] [client 10.10.31.54:59864] AH01276: Cannot serve directory /var/www/gestsup/upload/: No matching DirectoryIndex (index.html,index.cgi,index.pl,index.php,index.xhtml,index.htm) found, and server-generated directory index forbidden by Options directive
[Thu Jul 25 14:33:40.319542 2019] [:error] [pid 27890] [client 127.0.0.1:39236] script '/var/www/html/admin/api.php' not found or unable to stat
[Thu Jul 25 14:33:40.390935 2019] [:error] [pid 4732] [client ::1:55496] script '/var/www/html/admin/api.php' not found or unable to stat