I had trouble a month or so ago when I was asked to update my payment information when there was actually nothing wrong with my payment information. I ended up adding PayPal just to get rid of the annoying flag, which it did.
Now, my wife – through family sharing – is also being told to "update payment information", which clearly shows my (valid) payment information.
I have tried:
Updating my payment information (again)
Removing and re-adding my wife from family sharing
… to no avail: she still has a red flag and is being refused purchases.