Hi Florent,
This is not normal, in app purchases have to be active for all email in the family. Photon allows family sharing.
I will send you a workaround if it doesn’t work but I can’t do that before tomorrow.
Sorry
I’m having this problem as well. I purchased the app on my wife’s account with my card. I have been using it on an iPad with my account as well, but after deleting and reinstalling during troubleshooting I have been unable to restore the purchase and am stuck with 16 channels. Can I get some help with this?
Edit: I did resolve this by logging off of the iPad, logging in with her account, restoring the purchase, then switching back. Not super smooth but a workable solution.