There used to be two apps:
CBS All Access (subject of this thread)
CBS All Access became Paramount+ so now there are:
So now people search for CBS and find this thread, which is old and really much more related to Paramount+ and they probably waste a lot of time reading fixes that don't apply to the app they’re using.
For @houndish If you've already tried the usual: remove the channel, reboot the Roku (don't skip this), add the channel back, and it still doesn't work, then it's time to contact CBS about that.