I would try to fix list of "Available software sites" in preferences. See
"Install/Update->Available Software Sites" category. Make sure you have
"https://devstudio.redhat.com/updates/8.0/" in list and it is selected, remove
sites you mentioned in your question, save your changes and check for updates again
through "Help->Check for Updates".
Posted by forums
Original post:
https://developer.jboss.org/message/913749#913749