This has been affecting me for the same amount of time as everyone else, so frustrating, so I asked my contact at Handelsbanken, this is their reply:

I have looked into this for you and we are aware that there is an issue however the problem if with Quickbooks rather then us.  The latest update we have was on the 5th February.

Quickbooks advised us that they believed that they had found the problem and they were planning to deploy a fix on the 10th February which they are hoping will resolve all the issues our customers are facing.

It may be worth waiting until the 11th February before you try to log on again