When you check for updates via the Help menu, OSATE contacts all registered update sites. If one of them is not reachable at the time or does no longer exist, the update fails.
You can look at the error messages and find the offending update sites and disable them in the settings.
Alternatively, as the only plugin that can be updated at this time is the JVM, you can update it via Help > Install New Software...
"JustJ Adoptium OpenJDK Hotspot JRE Complete Stripped" as the runtime environment to install/update.
Then uncheck "Contact all update sites during install to find required software", and proceed. This way OSATE will not try to reach unavailable update sites and should install the latest Java 17 JVM without an error. I just tested and successfully updated to 17.0.15.
Most features and plugins on OSATE are locked to a specific version, so they cannot be updated. This is to avoid breaking functionality by changes in a new version of a plugin. Unfortunately we don't have the time to test old OSATE versions against updated features and plugins.