Message saying i need to UPGRADE to talk in discussion channels

HI, i have leveled a 15commander as first asked, then when i was able to be added to discussino channels, first it was not possible to add me and when someone finally added me, when i write, they can’t see it, i can’t see the private group discussion channel posts and a message pops up as soon as i wrote saying "you need to upgrade in order to be able to tchat in private discussion channels.
So i can write and see posts in arcade channel for example, the main channels of SC2, but when i want to do the same and be added in private ones, i got this message.
Can someone help me please?
i already did other steps like reuploading the game, the battle.net agent…
did someone experience the same thing and know how to correct it please? thank you