I have installed the Upgrades plugin. No problems.
Installed Upgrades Advertising. No problems until I looked at a blog and see this error message:
Fatal error: Call to undefined function upgrades_show_ads() in /home/.../domains/.....com/public_html/wp-content/mu-plugins/upgrades-advertising.php on line 123
Remove 'upgrades-advertising.php' from '/wp-content/mu-plugins' and error goes away.
Is it possible that I have overlooked something when I installed Upgrades?
Edit: I think that I have answered my own question. I will check. I didn't create the directory '/wp-content/mu-plugins/upgrade-plugins'plugins.