I need to debug my Mobile app and webs based application

This is a repeat request owing to the first choice not having the required skills or unable to locate source code
General information for the website: Mobile app and web based application for ordering taxi's online. Includes multiple databases, gps tracking, operator/driver and customer registration and password recovery
Kind of development: Customization of existing website
Num. of web pages/modules: A lot
Description of every page/module: ecabs4u.com is a holding wordpress site that does not need work. The application is installed and live on https://ecabs4uaspx.com/Account/Login.aspx Mobile apps are available (Android and ios) from the usual app stores
The basic operation of the system is Customers have 2 basic choices to make. Whether they need a cab 'Now' or 'Later' the system reacts differently according to certain parameters. the job is circulated to drivers. Drivers enter the fixed price that they will carry out the journey for and the customer can select the bid he prefers and the driver acknowledges he will carry out the transfer. At this time a direct debit is triggered to pay us our commission
Description of requirements/features: I require you to familiarise yourself with the entire system and debug it where I ask you to and indeed, wherever you discover any errors. At present the only bug that is preventing use of the system is occurring when a customer searches for a 'Cab Now' job. The system is throwing up a warning 'Insert error 2'.
There are other administration bugs present which will be very simple to repair. These are not vital.
Unfortunately the company who developed this application have ceased trading and left me in the lurch.
There are further development opportunities that you will be most eligible upon successful repair of the application
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