As you might already know, locally hosted/deployed Applications are limited to the office local network and cannot be accessed outside the Office Network directly. This is the reason why Testsigma Servers cannot access these applications directly and testing local application using Testsigma Labs fails.
There are 2 possible ways in which you can test locally hosted applications using Testsigma.
1. Hybrid Execution
Hybrid Executions are nothing but local executions that uses the local machines to run the tests instead of the devices available on cloud(Testsigma Labs is the default Test Lab Type and it uses Cloud devices). You need to install a small utility named 'Testsigma Agent' to enable Hybrid Executions on a machine.
Once Testsigma Agent is set up, there are no additional configuration required since the application is already accessible on the local machine and the tests are also run on the same machine.
Please check the articles given below for instructions on installing Testsigma Agent.
2. Sauce Connect
If you have a Sauce Labs account, you can use 'Sauce Connect' utility to create a tunnel that allows executing your local application on Sauce Labs' cloud machines.
Note: The above two solutions would work in the case where the application is restricted by Network Firewall as well.
Note: If your application is accessible online but can only be accessed by certain IP ranges as restricted by the Admin team, the easiest solution would be to whitelist the Testsigma IPs.