start by following the guide in this thread - Troubleshooting SmartThings Hub 2018 and Aeotec Hub . Do a search for your Router in that thread in case someone else has already posted how they got it to work. If you are still not able to get it connected, you will need to gather the hub logs and give to ST. You can find posts from @nayelyz and @Itati who have posted details on gathering the logs in their posts in that thread.
- make sure you are resetting the hub properly. Ethernet need to be connected between hub and your network when resetting.
- remember to remove the port block right after adding it to the app and it starts the download of the hub update.