Bad news: Firefox does not run the Java plugin (JRE) after Firefox 52.

Good news: WebTrader has a new version that no longer requires the JRE. In fact, FDA says

Attention WebTrader Users!
The FDA ESG WebTrader users are recommended to upgrade WebTrader client by November 30, 2018.

• https://www.fda.gov/ForIndustry/ElectronicSubmissionsGateway/default.htm

• https://www.fda.gov/ucm/groups/fdagov-public/@fdagov-afda-fda4you/documents/document/ucm537998.pdf

So it sounds like time to get busy!!

Thanks for your quick reply! But I am running a Webtrader version downloaded a couple of minutes ago... still the same ...

This isn't the type of application that forum volunteers can get hands on. FDA says you can use Firefox. So... how about some random guesses?

I notice toward the bottom of page 8 of the manual that a local certificate needs to be installed. Unless that also installed in Firefox, you would expect to get an "untrusted connection" error page when accessing a server which uses a certificate that was signed by the locally installed certificate. Have you seen an error like that?

If you exit out of Firefox and start it up again, does it detect any new add-on that may have installed with WebTrader which allows communications between Firefox and WebTrader?

Otherwise:

If a site is generally known to work in Firefox, these are standard suggestions to try when it stops working normally:

Double-check content blockers: Firefox's Tracking Protection feature and extensions that counter ads and tracking may break websites that weren't built to operate normally without the blocked components.

Do you see a shield icon toward the left end of the address bar, near the lock icon? More info on managing the Tracking Protection feature in this article: What happened to Tracking Protection?.

Extensions such as Adblock Plus, Blur, Disconnect, Ghostery, NoScript, Privacy Badger, uBlock Origin or uMatrix should provide toolbar buttons to manage blocked content in a page. There may or may not be a number on the icon indicating the number of blocked items; you may need to click the button to see what's going on and test whether you need to make an exception for this site.

Cache and Cookies: When you have a problem with one particular site, 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.

(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 > "Clear Cookies and Site Data"
• (menu bar) Tools > Page Info > Security > "Clear Cookies and Site Data"
• click the padlock or "i" icon in the address bar, then the ">" button, then More Information, and finally the "Clear Cookies and Site Data" button

In the dialog that opens, you will see one or more matches to the current address so you can remove the site's cookies individually without affecting other sites.

Then try reloading the page. Does that help?

Testing in Firefox's Safe Mode: In its 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. (On Mac, hold down the option/alt key instead of the Shift key.)

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

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

... unfortunately no improvment ... Still wondering why it works with IE and does not with Firefox... Another strange issue is that "http://localhost:8091/security/trust?requestUrl=https%3A%2F%2Fesg.fda.gov%2FsendDocument", FDA´s proposal to solve this issue, is regarded as unsafe and not even opened... Highly appreciate all your kind effort! Not even FDA-Helpdesk can help me out. And in the very end there is a small checkbox somewhere that needs to be unchecked... computers ...

Sorry, but that online manual is all I know about that program. Hopefully you'll figure it out.