Kami on iMac 27 inch

So…I have Kami all set up to be used in Canvas by my students. It works fine on various devices, but I just bought an iMac 27 inch (5K display) and Kami displays at 25% of the right size on the iMac. The iMac displays the same documents in the right size outside of Kami. So the problem is some sort of Kami-plus-iMac 5K issue. Anybody know what to do?

https://community.kamihq.com/u/Chamomile who are you