.NET 4.8 Missing
When attempting to install NHS Credential Management, you may see the following error:

This happens when the machine does not have .NET Framework 4.8 installed.
To resolve this, install .NET Framework 4.8 and try again.
Multiple versions installed
NHS Credential Management does not currently remove any previously installed versions prior to installation of a new version. Instead, attempting to run both versions simultaneously will display an error saying that the application is already running.
Should multiple versions be installed, remove all installations of NHS Credential Management. Once all existing installations have been removed, the correct version of NHS Credential Management can then be installed.
NHS Port Service not running
If the NHS Port Service is stopped and a user attempts to access Spine or any application, they may see the following error:

To fix this, navigate to Services with admin privileges and search for NHS Port Service. Start the NHS Port Service and then NHS Credential Management should start without issues.
It is mandatory to keep the NHS Port Service running always while using NHS Credential Management. So, to avoid this error it is recommended to never stop the NHS Port Service manually.
Windows credential prompt while accessing web applications

If you see this prompt, the machine is not configured correctly to use NHS Credential Management. To fix this, go to the configuration section of this guide and follow the instructions there.
If the issue is still not resolved then try the following steps.
Local Intranet Zone settings
Use the Windows start menu to navigate to Control Panel >> Internet Options. Go to the 'Security' tab and select 'Local intranet', and then the 'Sites' button.

Verify the checkboxes are as shown in the image below.

Select 'OK' to exit that window, and then select 'Custom level'.

In the 'Security Settings - Local Intranet Zone' window, scroll to the bottom and under 'User Authentication', make sure 'Automatic log-on only in Intranet zone' is the option selected.

Select OK to exit the window. This should be all that's needed for NHS Credential Management to work.
If the issue persists, continue below.
Trusted Sites Zone settings
In the 'Internet Properties' window, select 'Trusted sites', and then the 'Sites' button.

Step 1: Check to see if any of the following entries are there in the websites list (do not modify the list):
- https://localhost
- http://localhost
- localhost
These entries are not needed for NHS Credential Management. If none of them are present, then move to the section below on restricted site zones. However, if one or more than one of these entries are in place for other reasons, then move on to step 2 below.
Step 2: In the 'Internet Properties' window, with 'Trusted sites' still selected, select the 'Custom level' button.

In the 'Security Settings - Trusted Sites Zone' window, scroll to the bottom and under 'User Authentication', make sure 'Automatic log-on with current username and password' is the option selected.

Select OK to exit the window, then try starting NHS Credential Management again.
If the issue persists, continue below.
Restricted Sites Zone settings
In the 'Internet Properties' window, select 'Restricted sites', and then the 'Sites' button.

If any of the following entries exist in the websites list, remove them and click the OK button.
- https://localhost
- http://localhost
- localhost
NHS Port Service start-up failure on VDI environment

On a VDI system, if the user is prompted with the above exception while the system is booting up and the user is using NHS Credential Management version less than 1.1.0.0, then follow these steps:
- Stop the NHS Port Service.
- Delete the following files.
- C:\Program Files (x86)\NHS Digital\NHS Port Service\PortStore.txt
- C:\Program Files (x86)\NHS Digital\NHS Port Service\DomainList.txt
- Recreate the VDI image.
Note: CMS (Card Management System) operations are still not allowed on Citrix / VDI / Terminal Services.
No PIV mini driver

This error can be caused by a missing PIV mini driver.
Download the latest Microsoft PIV mini driver, install it with administrative rights, and restart the system. Check the PIV mini driver is present at the following system path (note the file path is named 'civ', not 'piv'):
C:\Program Files (x86)\CivMinidriver
Locked smartcard (series 9 only)
If you fail to enter the correct passcode via the contactless method, you will reach your maximum retries after 7 failed attempts. Should this happen, you can try an additional 3 attempts via contacted to recover the smartcard.
If your card is locked you can use self-service smartcard unlock.
If you cannot use self-service smartcard unlock then you will need to seek help from your Registration Authority to unlock your smartcard.
By default, the values set for contacted attempts is 10 and 7 via contactless.