When someone is filling out the submission form, it is NOT sending out an email or storing the submission anywhere.

I have confirmed all files of version 4.0 on 1.5.7c are properly installed and present. From Extras>Links Contact, I sent a test email to a manually added link recipient. The Subject was TEST and the body was TEST, here is what was received and I received an error log:

Click image for larger version. 

Name:	Screen Shot 2021-07-09 at 5.48.42 PM.jpg 
Views:	128 
Size:	60.4 KB 
ID:	19667

[09-Jul-2021 22:41:59 UTC] Request URI: /xxxx/index.php?cmd=links_contact&action=send_email_to_user, IP address: 184.170.174.172
#1 substr() called at [/includes/functions/functions_email.php:587]
#2 zen_build_html_email_from_template() called at [/includes/functions/functions_email.php:109]
#3 zen_mail() called at [/xxxx/links_contact.php:34]
#4 require(/xxxx/links_contact.php) called at [/xxxx/index.php:11]
--> PHP Warning: substr() expects parameter 1 to be string, array given in /includes/functions/functions_email.php on line 587.

[09-Jul-2021 22:41:59 UTC] Request URI: /xxxxx/index.php?cmd=links_contact&action=send_email_to_user, IP address: 184.170.174.172
#1 mysqli_real_escape_string() called at [/includes/classes/db/mysql/query_factory.php:121]
#2 queryFactory->prepare_input() called at [/includes/classes/db/mysql/query_factory.php:515]
#3 queryFactory->prepareInput() called at [/includes/functions/database.php:54]
#4 zen_db_input() called at [/includes/functions/functions_email.php:432]
#5 zen_mail_archive_write() called at [/includes/functions/functions_email.php:381]
#6 zen_mail() called at [/xxxx/links_contact.php:34]
#7 require(/XXkcaz00/links_contact.php) called at [/xxxx/index.php:11]
--> PHP Warning: mysqli_real_escape_string() expects parameter 2 to be string, array given in /includes/classes/db/mysql/query_factory.php on line 121.