A device could not resolve cross-domain API URL
Cross-domain API is a mechanism which allows 3rd party solution interact with OPSWAT Client to get device ID for a device which OPSWAT Client is installed. Learn more details here.
OPSWAT Client uses eapi.opswatgears.com domain for this API and it should be resolved to a loopback IP address, for example 127.0.0.1.
If you try to resolve the domain eapi.opswatgears.com from a configured DNS server on your device and you get no result or it’s in correct. Please contact your administrators to solve the problem.
While waiting for a permanent solution, you can add that domain to a hosts file on your device as a workaround solution by following the below steps.
On Windows Devices
Step 1: openWindows Start menu → search for Notepad → Choose Run as administrator

Step 2: Choose File → Open

Step 3: Paste C:\Windows\System32\drivers\etc\hosts.txt at File name → Choose Open

Step 4: Add 127.0.0.1 eapi.opswatgears.com to hosts.txt → Save

On macOS Devices
Step 1: Launch Terminal
Step 2: Type sudo nano /etc/hosts and press Enter

Step 3: Enter your admin password
Step 4: Add 127.0.0.1 eapi.opswatgears.com to this file

Step 5: When finished, hit Control+O followed by ENTER/RETURN to save changes, then hit Control+X to exit out of nano
On Linux Devices
Note: these steps were recorded on Ubuntu. If you use different distro or version, the user interface can be different.
Step 1: Launch Terminal
Step 2: Typesudo nano /etc/hostsand press Enter

Step 3: Enter your admin password
Step 4: Add 127.0.0.1 eapi.opswatgears.com to this file

Step 5: When finished, hit Control+X and hit Y to save changes
Reference:
https://setapp.com/how-to/edit-mac-hosts-file
https://www.tecmint.com/setup-local-dns-using-etc-hosts-file-in-linux/