The [wp-members] shortcode tag was deprecated over two years ago and should be replaced with the more recent version, which in this case is [wpmem_form password]. See: https://rocketgeek.com/shortcodes/list-of-replacement-shortcodes/
However, the shortcode does actually work and the error you are receiving is not likely an issue as a result of the outdated shortcode.
The problem is most likely that there is an issue with the rows array for the form assembly. In the forgot password form, that is generally caused by running some functions from outside sources that are incompatible with each other and result in no form rows being in the array used by the form builder.
When I looked at the site, I can see that you are using the Email as Username extension (and also some others) so you must have been a premium support subscriber at some point. It’s possible that you have some incompatible settings and/or customization regarding having the forgot password reset be just the email address (instead of the username & email).
If you have a customization to have the password reset require just the email address (as a custom code snippet), that is the problem and it should be removed. Using the Email as Username extension does this automatically (since the username IS the email address), so if a custom code snippet is applied to do the same thing, it ends up removing the remaining form row, leaving the form with no input rows which causes the error.
Thank you, I change the old shortcode and disabled the Email as Username extension.
