Presuming you mean the stable version available from:
https://nvda-addons.org/files/get.php?file=rp
<https://nvda-addons.org/files/get.php?file=rp>
it pretty much must be whatever security suite you're using.  Windows
Security doesn't block it, but I can imagine that certain security
suites sensitive to the word "password" itself might flag it as suspicious.

It really is a security violation to have password characters echoed.
You should be able to override the block, but not knowing what security
suite you're using, and since I use Windows Security exclusively, I
cannot tell you how.
--

Brian -Windows 10, 64-Bit, Version 21H2, Build 19044

*/The real art of conversation is not only to say the right thing in the
right place but to leave unsaid the wrong thing at the tempting moment./*

        ~ Dorothy Nevill