Can you try the following.

1.
Clear the web browser cache.
For Internet Explorer 11
To clear the Internet Explorer 11 cache open “Internet Options” by pressing Alt + X or pressing the Tool icon on the top right hand of the window, select “Internet Options from the menu.

Select “Delete” from the Browsing history in the Internet Options dialog box.
In the “Delete Browsing History” dialog box Check the boxes for “Temporary Internet files and website files” and “Cookies and website data”, press Delete.

Press ok to close the “Internet Options dialog box”

Press the “x” on the “Internet Explorer has finished deleting the selected browsing history” status display to close.

If you need instructions for clearing Firefox or Google Chrome browser caches let me know.

Exit the browser, close all browser windows or select File -> Exit or Alt + F4.

2.
Clear the Java Webstart cache.
Start -> All Programs -> Accessories
Select "Command Prompt"
Enter the following command

"C:\Program Files\Java\jre7\bin\javaws.exe” -uninstall

or if using 64 bit Windows OS use
“C:\Program Files (x86)\Java\jre7\bin\javaws.exe” -uninstall

3.
Start your browser and browse to the the Omniscope online page, select Launch.
http://tc.visokio.com/webstart/version.jsp


If there are any errors can you take a screenshot of the error dialog box or the screen.

We also need to know the operating system and browser version that produces the error.

We have tested it successfully on Windows 7 Service Pack 1 and Windows 8.1 (32 bit) OS with both Internet Explorer 11 (11.0.9600.16476 Update 11.0.2) and Google Chrome (32.0.1700.76) , Omniscope Online starts and opens up correctly using the launch button from this page.

http://tc.visokio.com/webstart/version.jsp

This is the version of Java we have tested it on.
"C:\Program Files\Java\jre7\bin\java.exe" -version
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) Client VM (build 24.51-b03, mixed mode, sharing)

Hosting Omniscope Online

If using a custom jar please update the deployJava.js file on your own webserver to the latest version from Java. This will correctly identify Internet Explorer 11 "Trident" browser for Java Network Launch Protocol (JNLP).

Visokio Omniscope Custom Viewer Customisation
http://tc.visokio.com/customjar/index.jsp

Visokio Omniscope Custom Viewer Customisation
http://www.visokio.com/kb/custom-jar

The live deployJava.js version is available from Java here:
http://java.com/js/deployJava.js

Thanks Donald,

Unfortunately this doesn't help. What we have noticed is that 2.7 still works and 2.9 as well. The problem is only applicable to 2.8.
How can we solve this issue? Yesterday, everything worked fine and suddenly nothing works.....

I will send you the error message in a separate email.

Hope you can help. Always happy to share our server with you.

Thanks
A

Java Webstart requires a "signed" jar.

The signed jar from Visokio is available from the download page.
http://www.visokio.com/download/?platform=jar
http://downloads.visokio.com/omni28/auto/2-8_b1190/Omniscope.jar

Replace the custom jar on your webserver with the Visokio signed jar downloaded from the above page.

You can check using the webstart page at the url below which generates JNLP, code and and a link to webstart using the original signed jar on the Visokio servers.
In "Application Settings" "File to Open:" enter the web link to the IOK file to open.

http://tc.visokio.com/webstart/

The custom jars generated using the link below can still be run when downloaded and run locally.
http://tc.visokio.com/customjar/index.jsp

Hello Donald,

Is there also an original v2.9 signed jar available?

Yes.

http://www.visokio.com/download/zanzibar?platform=jar

There are some problems with 1227 (jxbrowser) and we will be updating the default version once it passes the extended testing session.

So please select Daily Builds and select at least version 1262 Omniscope 2.9 Alpha b1262 (Cross-platform JAR).
http://downloads.visokio.com/omni29/auto/2-9-alpha_b1262/Omniscope.jar

We have updated the default release to Omniscope 2.9 Alpha b1262 (Cross-platform JAR).

http://www.visokio.com/download/zanzibar?platform=jar