I also can’t click Don’t Allow - this dialog won’t go away no matter which one I click.
Update - I uninstalled, restarted, reinstalled, and all is good.
A classic “have you tried turning it off and on” situation.
I don’t know if it will help but are login and Local Items in Keychain Access locked or unlocked? In mine both are unlocked.
Edit: another thing to try is to quit Nord, then lock and unlock login and Local Items. I had a similar problem in the past and doing this resolved it. Otherwise it might be better to reinstall Nord after purging all related files.