Especially when card readers are connected via USB device server, the intervening network can lead to the timeout of 5 seconds being exceeded and Windows deregistering the signature card.
By adding / setting the registry key HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Cryptography\\Calais\\TransactionTimeoutDelay can be increased from the default of 5 seconds up to 60 seconds.
S. also. https://support.microsoft.com/en-us/help/2706168/applications-that-use-smart-card-authentication-stop-responding-on-a-c