Some add-ons are not active when using Private Windows.

Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; <Control> (Mac=<Command>) <Shift> A)

In the Add-ons Manager, on the left, select Extensions. Find and select that add-on.

Locate and select Run in Private Windows.

The problem is not related to an extension. If I disable the only extension I have active ("In Zoom") the problem still occurs.

We have seen several reports during the past months of this issue with pop-up blocking in Private Browsing mode.

• https://support.mozilla.org/en-US/search?w=2&product=firefox&q=field%3Acontent%3A%7Bpop-up+private%7D+range%3Aquestion_created%3Agte%3Anow-180d%2Fd&page=1

This is a deliberate decision that is the result of isolating normal mode and PB mode permissions. See:

• https://bugzilla.mozilla.org/show_bug.cgi?id=1702290#c3

See also:

• bug 1701814 - Popup exceptions set via about:preferences do not apply to private browsing windows

You could disable this isolate feature, but that can lead to other unexpected issues.

• bug 1692567 - Accessing a site in Private Browsing can cause that site's non-private session to be logged out in 24 hours

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)

@cor-el Thanks for that.

So the only solution currently until the UI for https://bugzilla.mozilla.org/show_bug.cgi?id=1589608 is sorted out is to turn the popup blocker off globally (which works, and I have now done)?

This presumably isn't the desired outcome that https://bugzilla.mozilla.org/show_bug.cgi?id=1702290#c3 ("We consider being prompted again in private browsing a privacy feature.") had in mind.