Apple ID access after OS upgrade
Hello, I have trouble accessing the iTunes store (or iCloud as it were) when asked to enter my account name and password. My access works on the other linked devices, desktop Mac computer and the iPhone, but not on the laptop (13 inch Mac Book Pro mid 2012) which I've upgraded to Mac Os Sierra. It gives me a warning message that "there was an error accessing the Apple ID Server". I've reset the password, entered the verification codes on all devices and followed the instructions but can't figure out where the trouble is for the laptop... Any ideas? Thanks.
MacBook Pro