I do NOT want a new wifi network - It goes through the whole process and then it cant find the Time Capsule - I rescan and no luck - I have reset three times -
A few things to check.....and consider:
Make sure that you are configuring the Time Capsule to "Join a wireless network"
You must know the exact type of wireless security setting that the wireless router is using in order to provide the Time Capsule with the correct settings to join the network. Most users know the name of the wireless network and password, but few know the exact type of wireless security that their router is using.
Without the exactly correct setting....the Time Capsule will never join the network and you must start all over with another configuration attempt.
As LaPastenagure notes, trying to configure the Time Capsule this way is not a good idea for most users.
It's difficult to set up....as you you have experienced....and the Ethernet ports are not enabled on the Time Capsule, so you are locked into wireless only backups with no ability to do large backups using the much faster Ethernet connection.