ISPConfig 3: Can only use suPHP!?

Hey everyone,
I hope you can help me with this one:

I am using ISPConfig 3 on an Ubuntu 14.04 machine and most of the time I use suPHP.
Now I tried to upgrade to PHP 7.1. But as this is only possible by compiling it on my own and using it with PHP-FPM, I did so.
So I compiled PHP 7.1 and installed it properly in ISPConfig3. I then switched to PHP-FPM, but now the PHP files are no longer executed by the server. Instead there is a download window poping up offering me to download the files.
Interestingly it says:

Code:

Type: application/x-httpd-suphp

I checked the vhost file and there it says nothing in regards of suPHP:

Code:

                <Directory /var/www/demo1.example.de/web>
                                # Clear PHP settings of this website
                                <FilesMatch ".+\.ph(p[345]?|t|tml)$">
                                                SetHandler None
                                </FilesMatch>
                                Options +FollowSymLinks
                                AllowOverride All
                                                                Require all granted
                                                </Directory>
                <Directory /var/www/clients/client12/web61/web>
                                # Clear PHP settings of this website
                                <FilesMatch ".+\.ph(p[345]?|t|tml)$">
                                                SetHandler None
                                </FilesMatch>
                                Options +FollowSymLinks
                                AllowOverride All
                                                                Require all granted
                                                </Directory>



                # suexec enabled
                <IfModule mod_suexec.c>
                        SuexecUserGroup web61 client12
                </IfModule>
                <IfModule mod_fastcgi.c>
                                <Directory /var/www/clients/client12/web61/cgi-bin>
                                                                                Require all granted
                                                                    </Directory>
                                <Directory /var/www/demo1.example.de/web>
                                        <FilesMatch "\.php[345]?$">
                                                SetHandler php-fcgi
                                        </FilesMatch>
                                </Directory>
                                <Directory /var/www/clients/client12/web61/web>
                                        <FilesMatch "\.php[345]?$">
                                                SetHandler php-fcgi
                                        </FilesMatch>
                                </Directory>
                Action php-fcgi /php-fcgi virtual
                                Alias /php-fcgi /var/www/clients/client12/web61/cgi-bin/php-fcgi-85.xxx.xxx.xxx-80-demo1.manuel-sohns.de
                FastCgiExternalServer /var/www/clients/client12/web61/cgi-bin/php-fcgi-85.xxx.xxx.xxx-80-demo1.manuel-sohns.de -idle-timeout 300 -socket /var/lib/php5-fpm/web61.sock -pass-header Authorization  -pass-header Content-Type
                </IfModule>
                <IfModule mod_proxy_fcgi.c>
                        #ProxyPassMatch ^/(.*\.php[345]?(/.*)?)$ unix:///var/lib/php5-fpm/web61.sock|fcgi://localhost//var/www/clients/client12/web61/web/$1
                        <Directory /var/www/clients/client12/web61/web>
                                <FilesMatch "\.php[345]?$">
                                                SetHandler "proxy:unix:/var/lib/php5-fpm/web61.sock|fcgi://localhost"
                                </FilesMatch>
                        </Directory>
                        </IfModule>



                # add support for apache mpm_itk
                <IfModule mpm_itk_module>
                        AssignUserId web61 client12
                </IfModule>

Further I have checked every other possible ways to execute PHP such as mod-php, but they all show the same result.
The only thing working is suPHP.

Any idea what happend here and where to look for the error?

 

This is from https://deb.sury.org/ :

If you update your Ubuntu you can use ready-to-install PHP packages from Ondrej Sury.
https://www.howtoforge.com/communit...and-additional-version-on-ubuntu-18-04.79621/
Since it is not safe to run Ubuntu 14.04 anymore, I suggest you update and then use those PHP packages to get a working PHP and ISPConfig.
https://launchpad.net/~ondrej/+archive/ubuntu/php/

 

Thanks for your answer. The Upgrade is already scheduled but still 6 months away.
I can't do it right now, as this means a lot amount of work for me, which I can't pull off right now.

So I still have to fix this and upgrading is not really a choice. And there has to be a mistake somewhere as Fast-CGI and PHP-FPM were working in the past and I can't remember changing any of the settings.

It would be very helpful, if you have any hint to where I could look at. Right now I am pretty lost.