It is just because of a bad UI design change in the Creative Cloud app. You have to click on the tiny arrow at the right to get to see the app sections hidden beneath it. I almost get this question daily since Adobe changed the CC-App's design this way. 😕😕
---------Adobe Community Expert: "Gewusst wie, spart Energie." 😉
The beta tab used to be to the right, and would be hidden if the CC app window was not expanded enough to see all of the tabs. More recently, the beta tab was moved to the left end of the tabs because some people were having problems finding it. IME if the window was collapsed, it would default to show the left most tab, which is now the beta apps. You had to click on the '>' (greater than) character to reveal the Pre-Release tab.
Is your Creative Cloud app up to date? the Beta button used to get hidden behind the interface if you had the CC app collapsed to fit on your screen, but they moved it to the extreme left of the tab list so if you have All Apps selected, you should be able to see it.