Is this a form-based login, or a popup-style login?

Could you check for any internal error messages that Firefox might log about this problem? I suggest this method:

• Open the page where you are going to log in

• Open the Web Console in the lower part of the tab, either:
  • Ctrl+Shift+k
  • menu button > Developer > Web Console

• Click the little garbage can on the console's button bar to clear the existing messages

• Then try logging in, and check for any new messages in the console -- anything interesting?

More generally, when you have a problem with one particular site that previously worked normally, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Clear Firefox's Cache

See: How to clear the Firefox cache

If you have a large hard drive, this might take a few minutes. If you do not see the number going down on the page, you can reload it using Ctrl+r to check progress.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, try either:

• right-click (on Mac Ctrl+click) a blank area of the page and choose View Page Info > Security > "View Cookies"
• (menu bar) Tools > Page Info > Security > "View Cookies"
• click the padlock or "i" icon in the address bar, then the ">" button, then More Information, and finally the "View Cookies" button

In the dialog that opens, the current site should be pre-filled in the search box at the top of the dialog so you can remove that site's cookies individually.

Then try reloading the page. Does that help?

If no luck so far, could you test in Firefox's Safe Mode? In Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

Good afternoon jscher2000.

When trying to enter the password for 192.168.2.1, the developer's console showed 3 messages: "password fields present on an insecure Page/Iframe/Form". You helped me so far, as I learnt a lot about Firefox' facilities and tools. Even in safe mode the pwd was rejected. for configuring my router i have to use IE, what i really disklike.

kind regards.

Gert Gropp.

Is the router login page in HTTPS? If yes, maybe the SSL certificate is outdated and unsupported by Firefox.

Hi Gert, "password fields present on an insecure Page/Iframe/Form" sounds more like a warning than a block. Especially if Firefox lets you submit the form anyway.

To see whether it is a frame, if you right-click a blank area of the page near the login fields, does the menu include a "This Frame" item? If it does, you could try "Open Frame in New Tab" and see whether Firefox behaves any differently when the page is not framed.

Many thanks, but even within a new the pwd is still rejected. kind regards Gert

Many thanks, but "speedport.ip" or "192.168.2.1" is invoked under HTTP. Kind regards. Gert.

Nothing leaps to mind. Could you check with the vendor on whether this is a known problem with Firefox 48?

many thanks for your efforts and kind regards. Gert.

Unable to delete this post, my apologies. Edited version posted below.

Same problem here, but with Linksys WRT120N Home Wireless Router. Tried numerous fixes suggested by manufacturer technical support team, but all failed. Fortunately, the setup page is still accessible using Chrome, both on the same desktop and other mobile devices.

Similar problem here, but with Linksys WRT120N Home Wireless Router. Username and password input rejected every time even though I know they are correct. Tried numerous fixes suggested by manufacturer technical support team, but all failed. Fortunately, the setup page is still accessible using Chrome, both on the same desktop and other mobile devices.