Hmm, how odd! I’ve been testing around on our end on a Windows 10 machine with an external monitor but haven’t been able to reproduce the issue. While there was a bug where opening dialogs and popup windows caused Axure RP to get sent behind other application windows in build 3636 and earlier, we released build 3641 today with a fix to resolve those types of issues. If you haven’t updated already, I’d like to verify whether build 3641 also addresses the issue that you’re seeing with the Find and Replace dialogs not showing up at all.
If it is still not showing up after the update, then would you mind confirming the display settings and layout of your monitors? If you right-click the desktop and open Display Settings, I believe it should show which monitor is your primary, secondary, and tertiary monitor, as well as how they’re laid out in relation to one another; confirming this setup as well as which monitor you use Axure RP on (and whether it’s in full screen mode) would help to reproduce the issue. We have seen and resolved another bug where popups such as the action list for interactions would render in the wrong place at the wrong size if external monitors were laid out in a top-down order in Display Settings (such that you would drag windows up and down to get between monitors), so this would be good to confirm whether there’s a similar issue happening with the Find and Replace dialogs as well.
We’ll keep an eye out!