https://help.tallysolutions.com/docs/faqs/all_releases/5144.html

Error Tranmgr.900 or Linkmgr.900 or Manager.900

Upgrade to release 6.4.1 or later, and rewrite your data to resolve this issue.

Cause

While selecting a company in Tally.ERP 9, this message appears when data files are corrupted.

Solution

Back up your existing Tally.ERP 9 data.

· If you have recently taken a backup of your Tally.ERP 9 data, then restore your data and continue.

· If you have not recently taken a backup of your Tally.ERP 9 data, then rewrite your data.

If this error still appears, contact Tally Solutions.

How to prevent this error

Disable offline files on the server and client computers.