My YunoHost server
Hardware: VPS bought online
YunoHost version: 11.0.11 (stable)
I have access to my server : Through SSH | through the webadmin
Are you in a special context or did you perform some particular tweaking on your YunoHost instance ? : no
If your request is related to an app, specify its name and version:
My Webapp 1.0~ynh12
Description of my issue
I want to use the config panel on My Webapp. I get the following text hastebin in a popup. This has been the same since install and a couple of updates (although not to the app from memory). The configuration on install has been with no mysql and no php. I have done a test install with php 7.4 selected (as i thought that might be the bug) but that has made no difference.
There are a couple of similar posts I have found but their error is “Les versions du panneau de configuration ‘0.1’ ne sont pas prises en charge.”, not “Config panel question ‘fpm_free_footprint’ should be initialized with a value during install or upgrade.”
This is now solved but may be helpful to others with the same problem.
The bug for this version was posted on github at "500" Internal Server Error when trying to access config pannel from webadmin · Issue #97 · YunoHost-Apps/my_webapp_ynh · GitHub with a solution of ssh’ing in and forcing an upgrade of the app with
sudo yunohost app upgrade my_webapp -F
for each installation of the app (eg; replace my_webapp with my_webapp__2 if that is the installation.)
The forum that lets you solve your own problems is really the best type! 
[GET] /apps/my_webapp__4/config-panel?full
YunoHost encountered an internal error
Really sorry about that.
You should look for help on the forum or the chat to fix the situation, or report the bug on the bugtracker.
The following information might be useful for the person helping you:
Error: "500" Internal Server Error
Action: "GET" /yunohost/api/apps/my_webapp__4/config-panel?full&locale=en
Error message:
Config panel question 'fpm_free_footprint' should be initialized with a value during install or upgrade.