The most common reason for an "invalid" error is attempting to use a license key designed for an older (or newer) version of Horizon.
When copying a key from a PDF or an email, you often pick up a leading or trailing space. Try pasting the key into Notepad (to strip formatting) and then manually typing it into the Horizon Console. horizon connection server license key is invalid
Sometimes the Horizon Console UI hangs on old data. Clear your cache or try an Incognito/In-Private window. The most common reason for an "invalid" error