Thread:Project:Support desk/Mediawiki:sidebar substituted by default sidebar after upgrading

After upgrading to 1.21.1 from 1.17 the Mediawiki:sidebar has been substituted by the default sidebar. The wiki url is https://trv.jbv.no/wiki/ and the Mediawiki:sidebar is shown correct in https://trv.jbv.no/wiki/MediaWiki:Sidebar. However the default sidebar is shown as the menu. I use the vector skin but testing other skins has not helped. I don't find any other topics concerning this problem by searching the net/forums etc. Any suggestions of what went wrong in the upgrade? The rest seems to be in order.