I have been in touch with Jiri and dominic at support about this issue, my account is at shelter level 7 .
This is my 3rd season with this account, I bout legacy seasons for the last 2.
When I try to access seasonal challenges it always give me this message:
"Progress further through story challenges to unlock a gauntlet of season long challenges, these contain harder challenges..etc etc and unique mystery rewards etc etc"
I have uninstalled and reinstalled the game several times. please contact me
Thanks,
Steelskull Silvergoat