Errors associated with using the ID-card may be caused by browser configuration. It is possible that installation of different software has changed your browser settings and rendered logon with the ID-card impossible.
The simplest possible solution would then be the restoration of default browser settings.
For that, do the following:
1) Open Internet Explorer, select ‘Tools - Internet options’
2) In the new window select ‘Advanced - Restore advanced settings’ which brings up another window where you should click on ‘Reset’
Then close all open browser windows, insert the ID-card in the card reader, open the browser again and try authentication.
If the problem persists, turn to the ID-card helpline team by calling on 1777 ((+372) 677 3377 when dialling from abroad) or by sending an e-mail to firstname.lastname@example.org.