Since the new design of Viki not all channels can be followed like it used to be.
In the meantime use this detour
Go to
Explore
use the filters you need
if you look for new shows use the “new” filter
Than look for the 3 dots next to the channel you want to follow, click on it and click on the now showing “follow”
P.S. I decided to make a topic since so many ask repeatedly in the hope, this will help those searching for the function.
Hopefully Viki will find a more comfortable solution for this.
@jeslynl
Special thanks to @aznative who brought up this solution first.