I've tried updating my listing but there is no option to save the amends. Please help

Hosts report they are not able to save updates when they change their listing description. Save button is grayed out.

Save button inactive 

The reason is Airbnb has a hidden 500 symbols limit for the listing description. The Save button turns out once the content is larger than 500 characters and currently there is no symbol counter or warning message (as for the title field).

You will have to reduce the text and remove 1-2 sentences to 500 characters or fewer until the Save button is highlighted.

Unable to add a payment method?