I have an easy fix for this. All you have to do is disconnect both of your laptop and desktop from the third party (internet dongle, in your case) wifi hotspot. Now, in either one of your PCs, setup a WiFi hotspot. I assume you are using Windows 10 computers. To create WiFi hotspot for file transfers, follow these steps:
1: Go to Command Prompt in administrator mode (type Start+X) and click on Command Prompt (Admin)
2: Now in the command prompt, type this: netsh wlan set hostednetwork ssid=mynet key=password
3: In the above line of codes, replace mynet with your choice of name for the hotspot name and replace password with your choice of password for that network.
4: Once your hotspot is setup, you have to start that network, by typing the following codes: netsh wlan start hostednetwork
5: Now your WiFi hostpot is ready. Now exit the command prompt. The new WiFi network is now visible on your laptop/desktop (another PC). Connect it with the password and go to "Network" in file explorer and you will find your PC names there.
This answer would solve following common questions:
1: How to wirelessly transfer files between laptop and desktop?
2: How to wirelessly transfer files between laptops through wifi hotspot?
3: How to create WiFi hotspot on Windows 10 laptop?
4: WiFi file transfer between my computers is slow on a hotspot network, how to make it fast?