New WP install; no plugins active; cannot activate Security; 404 Error

ERROR LOG:
[05-Sep-2018 01:17:40 UTC] PHP Deprecated: Automatically populating $HTTP_RAW_POST_DATA is deprecated and will be removed in a future version. To avoid this warning set ‘always_populate_raw_post_data’ to ‘-1’ in php.ini and use the php://input stream instead. in Unknown on line 0

DEBUG LOG:
[15-Sep-2018 03:05:19 UTC] PHP Notice: screen_icon is deprecated since version 3.8.0 with no alternative available. in /home/user/public_html/wp/wp-includes/functions.php on line 3856
[15-Sep-2018 03:05:19 UTC] PHP Notice: get_screen_icon is deprecated since version 3.8.0 with no alternative available. in /home/user/public_html/wp/wp-includes/functions.php on line 3856

PHP: 5.6

URL WHEN DISPLAYING THE 404 ERROR PAGE:
https://www.domain.com/wp/wp-admin/plugins.php?action=activate&plugin=better-wp-security%2Fbetter-wp-security.php&plugin_status=all&paged=1&s&_wpnonce=30e4cea069

ERROR LOG:
[05-Sep-2018 01:17:40 UTC] PHP Deprecated: Automatically populating $HTTP_RAW_POST_DATA is deprecated and will be removed in a future version. To avoid this warning set ‘always_populate_raw_post_data’ to ‘-1’ in php.ini and use the php://input stream instead. in Unknown on line 0

DEBUG LOG:
[15-Sep-2018 03:05:19 UTC] PHP Notice: screen_icon is deprecated since version 3.8.0 with no alternative available. in /home/user/public_html/wp/wp-includes/functions.php on line 3856
[15-Sep-2018 03:05:19 UTC] PHP Notice: get_screen_icon is deprecated since version 3.8.0 with no alternative available. in /home/user/public_html/wp/wp-includes/functions.php on line 3856

PHP: 5.6

CPANEL ERRORS:
2018-09-16 12:07:36.506024 [INFO] [68.103.64.85:51594:HTTP2-67] File not found [/home/user/public_html/404.shtml]
2018-09-16 12:07:16.255015 [INFO] [68.103.64.85:51594:HTTP2-17] File not found [/home/user/public_html/404.shtml]
2018-09-16 11:54:14.295230 [INFO] [68.103.64.85:51445:HTTP2-53] File not found [/home/user/public_html/404.shtml]
2018-09-16 11:40:59.657720 [INFO] [82.198.187.135:38026] File not found [/home/user/public_html/406.shtml]
2018-09-16 11:38:33.199214 [INFO] [36.89.39.10:56025] File not found [/home/user/public_html/406.shtml]
2018-09-16 11:32:28.679466 [INFO] [68.103.64.85:51310:HTTP2-17] File not found [/home/user/public_html/404.shtml]

I checked around the net and solutions are varied … corrupted .htaccess file … malware present … nothing really specific.

Web host is not having much luck pinpointing anything.

Don
Don