Sure, the new url is https://www.meteorite.bi/downloads/saiku-plugin-p7.1-3.90.zip
and, for a longer story, this is how I reproduced the error:
First go for the Community Version of Saiku:
Then tail -f ..../tomcat/logs/pentaho.log
You should see the lines
2019-01-18 08:48:32,747 INFO [org.pentaho.di] 2019/01/18 08:48:32 - download_and_install_plugin - Start of job execution
2019-01-18 08:48:32,751 INFO [org.pentaho.di] 2019/01/18 08:48:32 - PurRepository - Creating repository meta store interface
2019-01-18 08:48:32,828 INFO [org.pentaho.di] 2019/01/18 08:48:32 - PurRepository - Connected to the enterprise repository
2019-01-18 08:48:32,829 INFO [org.pentaho.di] 2019/01/18 08:48:32 - download_and_install_plugin - exec(0, 0, START.0)
2019-01-18 08:48:32,830 INFO [org.pentaho.di] 2019/01/18 08:48:32 - START - Starting job entry
2019-01-18 08:48:32,831 INFO [org.pentaho.di] 2019/01/18 08:48:32 - download_and_install_plugin - Starting entry [Download Plugin]
2019-01-18 08:48:32,835 INFO [org.pentaho.di] 2019/01/18 08:48:32 - PurRepository - Creating repository meta store interface
2019-01-18 08:48:32,843 INFO [org.pentaho.di] 2019/01/18 08:48:32 - PurRepository - Connected to the enterprise repository
2019-01-18 08:48:32,843 INFO [org.pentaho.di] 2019/01/18 08:48:32 - download_and_install_plugin - exec(1, 0, Download Plugin.0)
2019-01-18 08:48:32,844 INFO [org.pentaho.di] 2019/01/18 08:48:32 - Download Plugin - Starting job entry
2019-01-18 08:48:32,849 INFO [org.pentaho.di] 2019/01/18 08:48:32 - Download Plugin - Start of HTTP job entry.
2019-01-18 08:48:32,861 INFO [org.pentaho.di] 2019/01/18 08:48:32 - Download Plugin - Connecting to URL: http://meteorite.bi/downloads/saiku-plugin-p7.1-3.90.zip
2019-01-18 08:48:32,867 INFO [org.pentaho.di] 2019/01/18 08:48:32 - Download Plugin - Start reading reply from webserver.
2019-01-18 08:48:33,213 INFO [org.pentaho.di] 2019/01/18 08:48:33 - Download Plugin - Resource type: text/html; charset=iso-8859-1, last modified on: Thu Jan 01 01:00:00 CET 1970.
2019-01-18 08:48:33,219 INFO [org.pentaho.di] 2019/01/18 08:48:33 - Download Plugin - Finished writing 351 bytes to result file [/Users/virgilio/Documents/pentaho/pentaho-server/pentaho-solutions/system/plugin-cache/downloads/saiku-3.90_1547797712745.zip]
2019-01-18 08:48:33,223 INFO [org.pentaho.di] 2019/01/18 08:48:33 - download_and_install_plugin - Starting entry [Unzip]
2019-01-18 08:48:33,224 INFO [org.pentaho.di] 2019/01/18 08:48:33 - PurRepository - Creating repository meta store interface
2019-01-18 08:48:33,226 INFO [org.pentaho.di] 2019/01/18 08:48:33 - PurRepository - Connected to the enterprise repository
2019-01-18 08:48:33,227 INFO [org.pentaho.di] 2019/01/18 08:48:33 - download_and_install_plugin - exec(2, 0, Unzip.0)
2019-01-18 08:48:33,227 INFO [org.pentaho.di] 2019/01/18 08:48:33 - Unzip - Starting job entry
2019-01-18 08:48:33,230 INFO [org.pentaho.di] 2019/01/18 08:48:33 - Unzip - Starting ...
2019-01-18 08:48:33,232 INFO [org.pentaho.di] 2019/01/18 08:48:33 - Unzip - Processing row source File/folder source : [zip:${downloadDestination}] ... destination file/folder : [file:///Users/virgilio/Documents/pentaho/pentaho-server/tomcat/bin/${stagingDestination}]... wildcard : [null]
2019-01-18 08:48:33,244 ERROR [org.pentaho.di] 2019/01/18 08:48:33 - Unzip - ERROR (version 8.0.0.0-28, build 8.0.0.0-28 from 2017-11-05 07.27.50 by buildguy) : Can not copy file/folder [zip:/Users/virgilio/Documents/pentaho/pentaho-server/pentaho-solutions/system/plugin-cache/downloads/saiku-3.90_1547797712745.zip] to [file:///Users/virgilio/Documents/pentaho/pentaho-server/pentaho-solutions/system/plugin-cache/staging]. Exception : [
2019/01/18 08:48:33 - Unzip -
2019/01/18 08:48:33 - Unzip - Unable to get VFS File object for filename 'zip:/Users/virgilio/Documents/pentaho/pentaho-server/pentaho-solutions/system/plugin-cache/downloads/saiku-3.90_1547797712745.zip' : Could not open Zip file "/Users/virgilio/Documents/pentaho/pentaho-server/pentaho-solutions/system/plugin-cache/downloads/saiku-3.90_1547797712745.zip".
Actually the size of zip file is really suspicious. As well as the returned content type which is text.
And -indeed- the file contains
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>301 Moved Permanently</title>
</head><body>
<h1>Moved Permanently</h1>
<p>The document has moved <a href="https://www.meteorite.bi/downloads/saiku-plugin-p7.1-3.90.zip">here</a>.</p>
<hr>
<address>Apache/2.4.18 (Ubuntu) Server at www.meteorite.bi Port 80</address>
</body></html>
I tried to notify MeteoriteBI team.
Regards
Virgilio