So as an IT Security consultant, I am well aware that this issue is with quickbooks, not Handlesbanken. It needs a new application interface writing with the correct encryption techniques to work with Handelsbanken security, which is in itself not unusual, its all industry standard techniques.
In 340 days, we have been subjected to a novel virus pandemic that has hit the globe. Medical technicians have identified the virus protein and how it impact cells and the immune system, developed a vaccine based on the genetic sequencing of the virus RNA that is seemingly very effective, and delivered this solution to almost half of the country.
Meawhile, as you stated above, your engineers are still scratching their heads over this.
Good luck, lets hope you don't get any serious security issues!! :)
