Super Administrator Cannot View Users Settings

Nextcloud version: 16.0.5
Operating system and version: Ubuntu 18.04.1 LTS
Apache or nginx version: Apache/2.4.29 (Ubuntu)
PHP version: PHP 7.2.19-0ubuntu0.18.04.2 (cli)

The issue you are facing:
The users settings page (path ending in settings/users) is no longer loading for the super admin account. I had recently made some changes to users and performed an update to next cloud, not sure which was the trigger.

Is this the first time you’ve seen this error?: Yes. It was working correctly before.

Steps to replicate it:

  1. Log in to my nextcloud server via a web browser using the super admin account.
  2. Select the user icon in the very top right of the page.
  3. From the drop down menu select “Users”

Expected: See list of users
Actual: Page is blank except for the header.

Note: Other accounts can still view the page, but of course with limited access.

The output of your Nextcloud log in Admin > Logging:

[PHP] Error: PHP Startup: Unable to load dynamic library 'IcePHP.so' (tried: /usr/lib/php/20170718/IcePHP.so (/usr/lib/php/20170718/IcePHP.so: cannot open shared object file: No such file or directory), /usr/lib/php/20170718/IcePHP.so.so (/usr/lib/php/20170718/IcePHP.so.so: cannot open shared object file: No such file or directory)) at Unknown#0

GET /ocs/v2.php/apps/notifications/api/v2/notifications
from 71.63.36.105 by [redacted] at 2019-09-30T16:18:39+00:00

[PHP] Error: PHP Startup: Unable to load dynamic library 'IcePHP.so' (tried: /usr/lib/php/20170718/IcePHP.so (/usr/lib/php/20170718/IcePHP.so: cannot open shared object file: No such file or directory), /usr/lib/php/20170718/IcePHP.so.so (/usr/lib/php/20170718/IcePHP.so.so: cannot open shared object file: No such file or directory)) at Unknown#0

GET /ocs/v2.php/apps/notifications/api/v2/notifications
from 71.63.36.105 by [redacted] at 2019-09-30T16:18:09+00:00

The output of your config.php file in /path/to/nextcloud):
I’d rather not upload unless needed.

The output of your Apache/nginx/system log in /var/log/____:

tail -f error.log
PHP Warning:  PHP Startup: Unable to load dynamic library 'IcePHP.so' (tried: /usr/lib/php/20170718/IcePHP.so (/usr/lib/php/20170718/IcePHP.so: cannot open shared object file: No such file or directory), /usr/lib/php/20170718/IcePHP.so.so (/usr/lib/php/20170718/IcePHP.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
[Mon Sep 30 06:25:02.534055 2019] [mpm_prefork:notice] [pid 1341] AH00163: Apache/2.4.29 (Ubuntu) OpenSSL/1.1.1 configured -- resuming normal operations
[Mon Sep 30 06:25:02.534062 2019] [core:notice] [pid 1341] AH00094: Command line: '/usr/sbin/apache2'
[Mon Sep 30 06:48:45.568481 2019] [core:error] [pid 4293] [client 89.248.174.216:36388] AH00126: Invalid URI in request GET ../../etc/passwd HTTP/1.1
[Mon Sep 30 12:58:42.725771 2019] [php7:error] [pid 6440] [client 185.156.177.130:53708] script '[redacted]/wp-login.php' not found or unable to stat

Afaik, this error is related to a faulty PHP configuration in general and not Nextcloud. You should first fix the requirements or disable IcePHP to let your web server start without errors.