Hello Mike,
FOSSBilling does not do any kind of IP address limiting unless it is specifically configured to do so,
In this case, the message you are seeing is because FOSSBilling was configured to do so from the staff settings:

This features should only ever be used if you have a static IP address as otherwise you can have situations like now where you are locked out.
If you are unable to login to the administrator panel at all, you need to follow these steps to manually disable this functionality and allow all IP addresses once again:
- Login to your database.
- Go to the
extension_meta
table.
- Find the row where the
extension
column is mod_staff
and the meta_key
column is config
.
- Delete the
meta_value
column for that row. This will reset the staff settings back to default and allow you to login once again.