https://help.tallysolutions.com/docs/te9rel64/Data_Management/Connectivity_and_Compatibility_with_TS9.htm

Connectivity and compatibility in Tally.Server 9 Environment

Tally.Server 9 needs to be connected to the Internet for smooth operations which include user authentication and license management.

Connectivity

If Tally.Server 9 has not been connected to the Internet for 30 days , in the List of Tally.Servers in Tally.ERP 9, information on the number of days till surrender will be displayed ( Will be Surrendered after x day(s) ):

Users need to ensure that Tally.Server 9 is connected to the Internet to avoid License Surrender.

Incompatible version of Tally.Server 9 used with Tally.ERP 9

Tally.ERP 9 Series A Release 4.51 or a higher release will crash with the following error message if Tally.Server 9 Release 4.5 is used for data sharing:

Users need to upgrade to a higher release of Tally.Server 9 to continue working on Tally.Server 9 data.

Incompatible version of License Server

The following message will be displayed in Tally.ERP 9 Series A Release 4.5 if Tally.Server 9 Release 4.51 or a  higher release is used alongside License Server 7.8 :

Users need to upgrade to License Server 7.9 for smooth operations.

Incompatible version of Tally.Server 9 used with License Server 7.9

The following error message will be displayed in Tally.ERP 9 if Tally.Server 9 Release 4.5 is used alongside License Server 7.9 :

Users need to upgrade to a higher release of Tally.Server 9 for smooth operations.