I first saw this two years ago, and it’s still broken.
I renewed my membership on my iphone… when I log in and use my macbook it says i have 25km left… come on Zwift, fix this mess. This is now the 3rd year I’ve had the issue! For 15/month it seems you can fix this fundamental issue!
Did you subscribe by paying via iTunes instead of through Zwift directly? If so, you have to click “Restore Purchase” to activate your iTunes purchase in-game