In some cases, the Krisp drivers might go missing. You will see error signs on the Krisp mic and/or speaker. If you hover over the sign, the tooltip will tell you the following: "Krisp driver is not found. Please restart or reinstall Krisp to recover."
When can the problem happen?
There are different scenarios when the issue can happen. One of them is when you update your OS and the Krisp drivers are not set up correctly after the system restart.
Restarting the coreaudio of your device
Go to the Activity Monitor
Click on View >>> All Processes to see the processes for all the users on your device
Search for coreaudiod
Force Quit it
After it restarts in a few moments, check Krisp. The error should be gone.
Over-installing the Krisp app
If the coreaudio restart didn't help, download the Krisp app from here and over-install it without uninstalling the app.
Uninstalling and re-installing the Krisp app
If the two previous solutions didn't help, uninstall Krisp as shown here, download the Krisp installer from here and install again.