Hi Sunny!
Are you using named-user licensing with Survey123? If so it looks like you may need to first log into arcgis.com to enable the Survey123 license.
Try this:
- Log into arcgis.com
- Select "licenses"
- In the "Search add-on licenses" search bar type "Survey123
- "Survey123 for ArcGIS" should appear as a result, select "Manage"
- Search for the username that you would like to use Survey123 with
- There should be a radio button on the right hand side. Select that to authorize the license.
- A prompt should appear asking you if you would like to email the member (in this case, yourself). You can select yes.
- You should now be able to use Survey123! : )
Let me know if this works for you.