Maybe this post could help you: Hub v3 Connectivity Issues.
If it doesn’t connect successfully, I recommend reaching out to customer support through any of the following paths:
From the ST app
- Open the SmartThings app
- Go to the menu tab at the bottom-right corner.
- On this page, select the option “contact us” and then go to “Error reports”
- Select the topic related to your issue and follow the steps to submit your support request
Through the SmartThings Web page
- Enter this page
- Select the topic that is more accurate for your case
- Follow the steps presented to submit your support request