500 error when adding new Agent

[JhGreen11]

Good afternoon,

I have recently started a new job and have inherited an osTicket system, i'm new to this system so please bare with me if I don't provide all the relevant information off the hop.

The current situation unfolded when my manager attempted to create an agent account for myself, he clicked the Add agent button and was sent to a 500 error page.

Looking in the PHP logs (inetpub\logs\php), the only errors I see are the following:

[19-Mar-2021 17:20:01 UTC] PHP Warning: PHP Startup: Unable to load dynamic library 'pdo_firebird' (tried: C:\xampp\php\ext\pdo_firebird (The specified module could not be found.), C:\xampp\php\ext\php_pdo_firebird.dll (The specified module could not be found.)) in Unknown on line 0
[19-Mar-2021 17:20:04 UTC] PHP Fatal error: Uncaught ObjectNotUnique: One object was expected; however multiple objects in the database matched the query. In fact, there are 2 matching objects. in C:\inetpub\Sites\osticket\include\class.orm.php:1363
Stack trace:
#0 C:\inetpub\Sites\osticket\include\class.orm.php(606): QuerySet->one()
#1 C:\inetpub\Sites\osticket\include\class.user.php(681): VerySimpleModel::lookup(Array)
#2 C:\inetpub\Sites\osticket\include\class.ticket.php(3936): User::lookupByEmail('jsimone@cmha-we...')
#3 C:\inetpub\Sites\osticket\include\class.ticket.php(4108): Ticket::filterTicketData('Email', Array, Array, NULL)
#4 C:\inetpub\Sites\osticket\include\class.mailfetch.php(898): Ticket::create(Array, Array, 'Email')
#5 C:\inetpub\Sites\osticket\include\class.mailfetch.php(947): MailFetcher->createTicket(1)
#6 C:\inetpub\Sites\osticket\include\class.mailfetch.php(1027): MailFetcher->fetchEmails()
#7 C:\inetpub\Sites\osticket\include\class.cron.php(25): MailFetcher::run()
#8 C:\inetpub\Sites\osticket\include\class.cron.php(110): Cron::M in C:\inetpub\Sites\osticket\include\class.orm.php on line 1363

These errors look to be unrelated to our problem. In the Apache log, the only error is a certificate warning that has been going on for several months where as this issue has just started recently.

List of software on the system:
xampp - Only Apache is active
PHP - Looks to be 3 version installed, 7.3.20, 7.3.13 and PHP 4 which looks to run the interanet system.
MariaDB 10.4
Operating system is server 2016 with IIS

Any direction or guidance would be greatly appreciated as i'm unfamiliar with this software.

Thanks