Factory reset the TC.. and start again with a computer connected by ethernet to the TC.
To factory reset unplug the TC.. hold in the reset and power on again.. this requires 3 arms or a friend to supply the extra arm. You must not release reset until the TC front led flashes rapidly which takes about 10sec.
This will not do anything to your info stored on the TC.
I recommend you setup the TC now with fully compliant SMB names.. for everything.
TC itself, wireless with separate names for 2.4ghz and 5ghz and hard disk name.
Short, no spaces, pure alphanumeric.
Use only WPA2 Personal for security with passkey of 8-12 characters mix of pure alphanumeric characters.
You can also lock the wireless channel.. stick to 1, 6, 11 for 2.4ghz ... try each in turn.
5ghz is less of an issue as it doesn't penetrate as far.