Jon,
Got your diagnostic report. And yes, QRecall cannot start its privileged helper. You also have a lot of "not found" errors on your archives, but we'll need to straighten out the helper first.
This problem is always an installation problem. To gain elevated privileges, QRecall must request that macOS install a "privileged helper" on its behalf. Sometimes (and I'm not always sure why) this doesn't happen or it gets messed up. Once messed up, a new helper can't be installed and QRecall can't un-install itself (because un-installing requires the privileged helper). A true catch-22.
The fix is simply to manually uninstall QRecall. This takes a little bit of work, but I'll give you a shortcut.
The steps are in the help under QRecall > Help > Guide > Advanced > Uninstall > Uninstall QRecall (the hard way). There's also a
copy on the web.
As a shortcut, start by performing just steps 3 and 4. (I suspect this is the root of the problem.) After restarting, launch QRecall. It should prompt for you admin credentials and reinstall QRecall. If it doesn't prompt you, make sure QRecall > Preferences > Authorization > "Capture and recall using administrative privileges" setting is turned on.
If that doesn't solve the problem, perform the entire un-install procedure (make sure you skip the ? "dagger" steps and step 9, as you don't want to start over when you re-install). Restart again and then launch QRecall.
If this still doesn't solve the "can't launch privileged helper" problem, please send another diagnostic report (QRecall > Help > Send Report) and we'll dig deeper.