They were unnamed (empty name) but recognizable by their Location column.After saving, updating Mylyn and restarting eclipse, the Available Software Sites looked like this: Probably, my experience with this bug will be needed for someone (including myself too... So, I could to add one thing to the mentioned here answers.Note: a link to this dialog is also available in the Install New Software dialog. No repository found containing: osgi.bundle,oracle.eclipse.lib,184.108.40.206510191754 For Eclipse Neon I had the mentioned error for Mylyn.
The 500 Internal Server Error is a very general HTTP status code that means something has gone wrong on the website's server, but the server could not be more specific on what the exact problem is.
If the 500 Internal Server Error message is appearing at check out during an online purchase, it might help to realize that sales are probably being disrupted — usually a great incentive to the online store to fix the issue very quickly!
What usually works quite well is installing plugins via the Eclipse Marketplace.
Oh and sometimes this helps: Uncheck some options (like OSGI in your case).
Besides these workarounds, IMHO this requires a fix.
We're in 2019 now, surely there is a way to fix this recurring issue? if repo URL not found: skip and continue with next URL / update (without aborting as critical error and preventing any other update)? It is a cleaner / simpler solution than the workaround explained above (add trailing slash) and it worked for me...
In Internet Explorer, the message The website cannot display the page often indicates an HTTP 500 Internal Server Error.
A 405 Method Not Allowed error is another possibility but you can be sure by looking for either A rewrite error occurred during RQ_RELEASE_REQUEST_STATE notification handling. The rule is configured to be executed before the output user cache gets updated.
So either the failure is temporary and you should try again or you are out of luck and may have to use a manual installation procedure (download and unpack in plugins folder).
Maybe you can increase your success rate by adding the repositories that supposedly contain the artifacts in the 'Available Software Sites' dialogue. In fact, I would like to find a 'perfect' answer to this question myself.
On Juno (Build id: 20130225-0426), exporting update sites from 'Available software Sites", fixing the trailing "/" in the exported xml as described above, removing all sites and importing the fixed xml worked for me.