Snap 5.0 on UBUNTU 16.04 / Update Plugins not working

Hello,
On my ubuntu 16.04, I have installed the snap with ./esa-snap_sentinel_unix_5_0.sh
or ./esa-snap_sentinel_unix_5_0.sh -Dinstall4j.showProxyConfig=true

Then I launch snap:
$ snap via …Tools => Plugins => Update

I tried to update the available plugins but the installation of nbm modules was not executed.

For example, the SNAP Engine Kit Module Homepage: https: //sentinel.esa.int/web/sentinel/toolboxes/snap-engine-kit
shows the following message:
Oops, something went wrong. The page you were trying to access is (temporarily) unavailable.

And in the messages.log file (see below) there were some java.io.Exceptions:

INFO [org.netbeans.modules.autoupdate.services.InstallSupportImpl]: Cannot access http: //step.esa.int/updatecenter/5.0/snap/snap-engine-utilities-5.0.5.nbm
java.io.IOException: Cannot access http: //step.esa.int/updatecenter/5.0/snap/snap-engine-utilities-5.0.5.nbm
at org.netbeans.modules.autoupdate.services.InstallSupportImpl.copy(InstallSupportImpl.java:981)
[catch] at org.netbeans.modules.autoupdate.services.InstallSupportImpl.doDownload(InstallSupportImpl.java:733)
at org.netbeans.modules.autoupdate.services.InstallSupportImpl.doDownload(InstallSupportImpl.java:661)
at org.netbeans.modules.autoupdate.services.InstallSupportImpl.access$600(InstallSupportImpl.java:92)
at org.netbeans.modules.autoupdate.services.InstallSupportImpl$1.call(InstallSupportImpl.java:172)
at org.netbeans.modules.autoupdate.services.InstallSupportImpl$1.call(InstallSupportImpl.java:144)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

Instead, but I do not know if this can help to understand, I noticed that after installing sen2cor with anaconda2, the corresponding plugin is regularly installed.

I also tried downloading .nbm files and installing them via PLUGIN MANAGER unsuccessfully.

At last, I tried to run the command:
$ snap --nosplash --nogui --modules –update-all
Will update org.csa.rstb.rstb.op.polarimetric.tools@7.3.0 to version 7.3.5
Will update org.esa.s2tbx.s2tbx.s2msi.reader@5.0.0 to version 5.0.6
Will update org.esa.snap.snap.temporal.percentile@5.0.0 to version 5.0.5
….
….
Will update org.esa.s3tbx.s3tbx.fu.operator@5.0.0 to version 5.0.3
Will update org.esa.s1tbx.s1tbx.op.calibration@5.0.0 to version 5.0.5
updates=158
null
null
Establishing a connection …
Establishing a connection …
http: //step.esa.int/updatecenter/5.0/snap-extensions/rstb-op-polarimetric-tools-7.3.5.nbm
$
The program stop and quits.

what can I do?

Bye
Maurizio

Where have you found this URL? Actually this not known to me.
The Link http://step.esa.int/updatecenter/5.0/snap/ works and lists the modules

Maybe the server was just temporarily down or you behind a proxy.
Have a look at Tools -> Options -> WWW and configure the proxy.

Hello MARPET,
Thank you! It was easier than I thought…

The wrong links were visible in Tools -> Plugins -> Available Plugins,
but now, they are all updated, and therefore no longer visible.

I had printed a case earlier, see the figure below

Ciao,
Mau