Hi RC. I'm Greg, 10 years awarded Windows MVP, here to help you.
Is this 7Zip, because I've never seen a case of 7Zip file passwording fail in twelve years in forums? I use it myself almost every day for even longer without a single problem. Full guide here:
https://www.digitional.com/how-to-encrypt-and-p...
It sounds like the zip program is malfunctioning, if you cannot get the password box to stay open or find it by hovering your mouse on the open Windows icon on Taskbar to see if it's there to click and bring into focus.
So I'd reinstall the zip program by uninstalling it in App Settings, restart PC, then reinstall the zip program using a fresh download from their official webssite ONLY.
Feel free to ask back any questions. Based on the results you post back I may have other suggestions if necessary.
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