Some commons issues that often occur when using the ping-on-join feature, and full explanations for how to fix them!
This means Tippy was not able to create a webhook for the channel you are trying to configure ping on join in. To fix this issue, make sure Tippy has the correct permissions in the channel
Once you made sure Tippy has these permissions, you can add the channel to the setup again.
Tippy has an automatic built-in protection to remove channels it is not able to ping in. Usually this occurs when the webhook was deleted, when Tippy lost some permissions, or when the channel gets deleted. If this is the issue, follow these instruction.
Sometimes this occurs as a result from an internal error at Discord. This usually doesn't happen, but when it does, simply add the channel back to the setup.