JOSM Installed and does not work!

Today I installed JOSM and Java, but JOSM does not work! The following error occurs:

"JOSM versuchte auf folgende Ressourcen zuzugreifen:

Dies schlug allerdings auf Grund folgender Netzwerk-Fehler fehl

  • sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

Dies könnte mit falscher Proxy-Einstellung zusammenhängen. Möchten Sie die Proxy-Einstellung jetzt ändern?"

How can I fix the problem? Which Proxy should I take? Why can I work with Potlatch?

What Operating system exactly?

What JOSM version?

What Java version exactly?

Do you have any other Java Software that can access internet?

Operating system: Windows 10 Pro
JOSM: Version 15390
Java: Oracle, Version 8 Update 221

This is the only Java I have.

Strange that JOSM tries to connect to “http://…” instead of “https”.

Can you open these URLs in your browser?
Can you try to (re)install certificates from *.openstreetmap.de and *.openstreetmap.com ?

I’ve seen this ages ago when JOSM tried to connect over IPv6 when it found IPv6 available but not routing (a web search for “josm ipv6” will find various comments). Various things have been changed at the JOSM end since then though.

Concerning the error message. It is:

"JOSM versuchte auf folgende Ressourcen zuzugreifen:

Dies schlug allerdings auf Grund folgender Netzwerk-Fehler fehl

  • sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

Dies könnte mit falscher Proxy-Einstellung zusammenhängen. Möchten Sie die Proxy-Einstellung jetzt ändern?"

All links work, but the second and the third show just xml-code as no style-information is linked.

If this is not the first time that JOSM was installed on the system maybe a broken configuration exists. Try to start josm from a command line in debug mode and with a clean directory:

java -Djosm.dir.name=josm_dev -jar josm-tested.jar --debug > josm.log

If JOSM works with that command you should try to remove the old configuration. The command

java -jar josm-tested.jar --help

tells you the directory names.

If JOSM still doesn’t work please open a ticket here: https://josm.openstreetmap.de/newticket
and provide the content of the file josm.log and as well as the output of

java -version

The JOSM devs probably know what to do or where to look at.