Oh no! This is something we saw a while back with one of the macOS updates, what version of Snagit do you have? If you check for updates, there may be an update that will fix this. If not, you can open a support ticket and our tech support team can help you out.
I am now experiencing this as well. I'm running Mac OS 10.15.3 and Snagit 2020.1.1 (96029). While in touch with Techsmith tech support about it, I'm posting here as well in order or to (hopefully) find us a solution.