Steps to reproduce:

1. Follow instructions to setup Okta : https://www.zabbix.com/documentation/5.0/en/manual/appendix/install/okta
2. Files are stored in `/usr/share/zabbix/conf/certs`
3. We only adapt the `username attribute` setting to set it with value "username" and on Okta we added an attribute statement : 

        3. Enable Sign on `AuthN requests`

Result:
Login does not work : 

**

Expected:
Login works like when only `idp.crt` file is required. All files are stored in the same path but Zabbix seems not able to find the files `sp.crt` and `sp.key`. Same behavior if I edit `zabbix.conf.php` to explicitely set the paths.