1) PC clock settings might be changed. This behavior is to protect from re-use trial after 31 days from 1st trial installation.
2) PC component parts much changed (e.g. CPU, motherboard, graphics card, hard disk).
3) OS has been upgraded or re-installed.

GV License service is not running or service module file might not be installed

Confirm if FlexNet license service is running by following steps:

1) Run Windows Task Manager then go to [Services]
2) Confirm if FlexNet Licensing Service 64 has Running status

If the service doesn’t have Running status, right-click on the service then choose [Start]
If the service is not listed, it might be failed to install. In this case, follow below steps:

1) From Apps & features, uninstall EDIUS, Mync and GV License Manager with unticking “Deactivate license” option
2) Be sure that anti-virus or real-time scanning turned off
3) Run EDIUS installer

After above, try to activate EDIUS license

Network adapter that GV License Manager can use is not running 

GV License Manager only supports built-in or PCI-e ethernet adapter USB adapter cannot be used for license validation

Use built-in or PCI-e ethernet adapter

1.Your internet connection might not work properly.
2.Firewall or anti-virus might block the internet connection.

Firstly, attempt to connect to the FlexNet portal site(https://activation1.grassvalley.com) with Internet Explorer. If you can see the log-on screen of the site, close it and then go to below for next troubleshooting.

1) Turn off Windows Firewall and then activate or de-activate the license.
2) Disable real-time scan of anti-virus and then activate or de-activate.
If the error still appears or you cannot access to the portal site, attempt off-line activation or deactivation.
3) Re-try license activation / deactivation after several minutes.

Incorrect EDIUS serial number might be entered for activation or deactivation.

Entered serial number was not found in the license server

Local ID file info might have a problem

If you want to delete your EDIUS license from the license list, delete it with below  procedure:

1) Request returning the license to your regional GV tech support along with target serial number and product name
2) Make sure that all other licenses have been deactivated (this will be required if another version of EDIUS has been activated)
3) In Windows Task Tray, right-click on GV License Manager icon then choose [Exit] to quit GV License Manager
4) Choose [Start] >  [GV License Manager] whilst pressing [Ctrl] + [Shift] key  
5) Right-click on GV License Manager icon then choose [License List]
6) Right-click the target license and then choose [Delete]
7) Quit GV License Manager (same step as #3)
8) Choose [Start] >  [GV License Manager] to restart GV License Manager
9) Retry license activation

All EDIUS licenses have been activated, but you tried further activation.

EDIUS allows to activate up to two licenses per one serial number, but you might try further activation

GV License manager allows to deactivate the license up to two times per one month. License deactivation tried exceeds this number.

Contact to your regional support along with EDIUS serial number

User tried on-line deactivation for the license that has been activated in off-line mode

Entered serial number is EDIUS Trial Version that has already been tried.