@Ruby2468 Hello Julia, 

If the tapo camera setup failed at the last step, please verify the WIFI password of main Router first 
Go to Settings-> WiFi on your phone, Tap (or Long press  the router's WiFi name  ->Forget / Delete the network 
Please reconnect to your router Wi-Fi and it will ask for a password, will it accept your router password?

Here is an FAQ that introduces some basic troubleshooting, please give it a try: 

What should I do if I fail to configure Tapo Camera?

https://www.tp-link.com/en/support/faq/2747/

If no help, can you help us confirm the some details here:

LED status on the camera after set up failed: is it Red/  Green etc. 

Network topology & model number of the router:  for example router Model Archer C7  )))((( Tapo camera  

Tapo app version: 

Can you share  a photo of the Error message on the APP with us?