Unknown error / Error code 400: Expired or invalid signature

Some signers experience that they aren't allowed to sign. This results in a 'Unknown error' or 'Error code 400'. The cause of this issue is often that the certificate attached to the NemID only works for logging in to their net bank, E-boks and more. Please note that this is a simple task. You should expect to use 2-5 minutes to solve this. 

1. Navigate to NemID self-service at www.nemid.nu (you can only do the following on the danish self-service version).
2. In the left menu, click Mit NemID, then Forny NemID, lastly click the button Forny NemID. Can't find this option? Click here. 
   
3. Follow the process after clicking the button. 
4. Activate your new certificate by clicking activate

You can change the settings so that your certificate is automatically updated every 3 years (when it expires).

1. Simply click Redigér indstillinger under Forny NemID in the left menu. 
2. Mark Ja (Standard) 
3. Click Gem ændringer 

I am missing the option to renew my certificate

If you do not get the option to renew (forny) your NemID once you have logged in, you might not have had this certificate to begin with (note that this can only be updated on the danish version of NemID's self-service). To order a certificate go here. Unfortunately, this webpage is only available in danish.