Sometimes the customer network does not allow the connection to the LicenseSpring api.
Here we have some info on how it works and how to check the connection with the license server
LicenseSpring publishes a list of public-facing IP addresses in their publicly accessible FAQ document (FAQ | LicenseSpring) - see image below. LicenseSpring reserves the right to change these IP addresses:
34.250.134.210
34.251.49.36
52.18.228.254
54.78.102.217
2a05:d018:1735:a703::10
2a05:d018:1735:a702::10
If the customer is after a fully qualified domain name for their firewall they should allow https://api.licensespring.com:443
If the connection is ok, but it still not working, it would be worth checking the time on the machine having issues. We have seen issues where incorrect time prevents activation.