Of course you have recently moved to a new version of Confluence & are probably aware there are things to be fixed.
Just in case you are not aware, the downloads for Scala plugin nightlies & EAPs are very much a mixed bag at the moment. For example, on https://confluence.jetbrains.com/display/SCA/Scala+Plugin+EAP+15 there are bad entries for 188.8.131.52 and 184.108.40.206 . Then on https://confluence.jetbrains.com/display/SCA/Scala+Plugin+Nightly nothing since 1.6.62 works for me, in particuar 1.7.121 gives a 404. On https://confluence.jetbrains.com/display/SCA/Release+fixes all are broken, :( Some of the correct download URLs can be deduced, e.g. https://plugins.jetbrains.com/plugins/nightly/1347/plugin/download?updateId=20690 , but not all. As I say, a mixed bag.
I do realise that latest plugins can be downloaded by choosing the update source in Idea. But today, in the process of sorting out the right plugin for the 14.1.5 EAP I discovered some of the Confluence download pages are now broken.