Changing a payment method doesn't cancel your subscription on the spot. Your access stays active until your next billing attempt.
If that next attempt can't go through, the subscription will then be cancelled. So if you want to stay on Max, just add a working payment method back from the Subscription page before the next renewal date.
To update your payment method:
On Desktop
Log in to your Songer account
Click the person icon in the top-right corner
In the menu, select "Subscription"
Scroll down and select "Change payment"
Select new payment option: card or PayPal
Enter your new payment details
Hit "Update payment method"
On Mobile
Log in to your Songer account
Tap the three lines in the top-right corner
In the menu, select "Subscription"
Scroll down and select "Change payment"
Select new payment option: card or PayPal
Enter your new payment details
Hit "Update payment method"