Possible errors in the use of the electronic certificate
Skip information indexYour certificate does not appear in the Internet Explorer certificate selection window
If when the browser requests the electronic certificate, the selection window is blank and none appears, you should check that the electronic certificate is correctly installed.
If the certificate is not installed or is not installed correctly
Go to "Tools", "Internet Options" and select the "Content" tab. Press the "Certificates" button and check the expiration date of the certificate. You can also access the certificate issuing authority's page to check if it is valid and has not been revoked. The certificate must appear in the "Personal" tab for the installation to be valid.
If the certificate had been imported from an invalid copy, it would appear in the "Other people" tab instead of appearing in the "Personal" tab and it would not be valid to access the procedures on the Tax Agency website. If so, check if you have a valid copy of the certificate. The icon for a valid copy will be an open yellow envelope with a certificate peeking out and a key, and the extension .pfx or .p12.
If the copy of the certificate is not valid (the icon is a green certificate and there is no key; the file extension is .cer) is because when exporting it, the "Export the private key" box was not checked, which is the personal information that the certificate contains and without which it is not possible to sign. If you do not have a valid copy that allows the certificate to be correctly imported (to the "Personal" tab), you must request a new certificate by repeating the entire obtaining process.
Whether the certificate is correctly installed
In order to perform the following actions, it is recommended to access Internet Explorer as an administrator. To do this, right-click on the Internet Explorer icon and press "Run as administrator" to open a window.
Access "Tools" in the menu at the top of the browser (or at the top right) and enter "Internet Options." In the "Security" tab, click "Reset all zones to default level"; Check the "Trusted Sites" icon and click the "Sites" button that is enabled to add the following address: https://*.agenciatributaria.gob.es/". The "Require server verification (https:) for all sites in this zone" box should be checked.
In the "Privacy" tab, uncheck the "Enable pop-up blocker" box. In the "Advanced" tab, click "Restore advanced settings."
Next, go to the "Content" tab and press the "Certificates" button. Select the certificate within the "Personal" tab and press the "View" button.
Within the "Details" tab, go to "Edit properties" and check the "Enable all purposes for this certificate" option. If there is more than one certificate installed on the computer, you can assign a name to each certificate that makes it recognizable when selecting it.
Accept the windows so that the changes are maintained and, back in the "Certificates" window, go to the "Trusted Root Certification Authorities" tab, since these actions must also be performed for the root certificate of the issuing authority. Select the root certificate of your issuing authority and double click on it (for example, if it is FNMT you must select the certificate " FNMT Class 2 CA", or "AC FNMT Users" if the certificate was issued on or after March 1, 2015).
Within the "Details" tab, go to "Edit properties" and check the "Enable all purposes for this certificate" option. Then press "OK". To finish, click "Apply" and "OK." For the change to be effective, it is necessary to close all Internet Explorer pages.
On Windows Vista or lower, the option within the "Details" tab to check "Enable all purposes for this certificate" is "Modify properties."