I personally haven't tested Net Express under 24H2 and you know that we will tell you to use Visual COBOL instead because the last operating system that Net Express was officially certified on was Windows 7.

It sounds like the upgrade process might have wiped out the license.
You can try to reset the license using the following instructions:

1. open up an administrative command prompt
2. Run the command: PROTCFG /FORCE_RESET
3. Select/Check Net Express under the Product column
4. Click on the Generate Reset License button
5. Make note of Request Reset Key
6. Leave the License Management System window while processing Request Reset Key
7. Submit the Reset Key to MF (send it via email to me)
8. Enter the Response Key from MF in the Response Key field
9. Close the License Management System window
10. Click Start > [All] Programs > Micro Focus Net Express x.x > Configuration > License Management System
11. Select/Check Net Express under the Product column
12. Click on the Generate Full License button
13. Make note of the Request Key
14. Submit the Request Key to MF (send it via email to me)
15. Enter the Response Key from MF in the Response Key field